Awesome Gamedev

A curated list of good stuff related to the development of games. This list
contains only free software for code, sellers who aren't evil for
physical resources, and free cultural works for assets.

I have also provided a list of resources which are not free, and the reasons
why, in the associated Wall of Shame file.

This is released under a Creative Commons-Attribution-ShareAlike license,
version 4.0. You can find its text in the LICENSE.md file.

This project is part of Peers - a community for growing freedom. Support
us today!

Table of Contents

• Assorted Assets
• Audio
  • Editors
  • Music
  • Sound Effects
• Communities
• Engines
  • General
  • HTML5
  • Physics
• Fonts
• Games
  • C
  • C++
  • CoffeeScript
  • Dart
  • ECMAScript
  • Java
  • Other/Multiple
  • Python
  • Scala
• Graphics
  • Assorted
  • Collections
  • Icons
  • Sprites
• Graphics Tools
  • Animation
  • Bitmap Compression
  • Editors
  • Mesh Tools
  • Spritesheet Tools
  • Texture Tools
  • Voxel Editors
• Learning Resources
  • Graphics
    • Beginner
  • Music
  • Programming
    • Beginner
    • Intermediate
    • Reference
  • Talks
• Programming Frameworks and Libraries
• Utilities

Assorted Assets

This contains collections of miscellaneous assets of different kinds.

• Openclipart - A giant collection of clip art. CC0.
• OpenGameArt.org - A large collection of art intended for game
  development. Various licenses, including free ones.
• Wikimedia Commons - A collection of various assets of all kinds. Various
  licenses, all CC or free-er.
• Open Source Game Clones - A collection of open source videogames that
  are clones of old games.

Audio

Editors

• Ardour - The digital audio workstation. GNU GPLv2 or later.
• Audacity - Software for recording and editing sounds. GNU GPLv2 or
  later.
• Beast - Music composition and modular synthesis
  software. GNU LGPLv3 or later.
• Hydrogen - An advanced drum machine, with a free drum kit
  included. GNU GPLv2 or later.
• LMMS - A digital audio workstation. GNU GPLv2 or later.
• MilkyTracker - Multi-platform application for creating .mod and .xm
  module files. GNU GPLv3 or later.
• Musagi - A large and sophisticated music editor. Expat.
• rFXGen - a tool to generate sound waves procedurally. zlib

General

• GameSounds.xyz - Royalty free music and sounds. Various licenses,
  including free ones.
• Musical Artifacts - A collection of music-related everything. Various
  licenses, all CC.

Music

• CC0 Music - A collection of music. CC0.
• ccMixter - A site for collaborating with musicians. Various licenses,
  all CC.
• Creative Commons on Bandcamp - Everything on Bandcamp under a
  CC-license. Various licenses, all CC.
• Creative Commons on SoundCloud - A Creative Commons collection on
  SoundCloud. Various licenses, all CC.
• Free Music Archive - An archive of free music. Various licenses, all CC.
• Incompetech - An artist providing royalty free music of all genres. CC-BY-3.0.
• Jamendo - A site providing music licensed under the Creatives
  Commons. Various licenses, all CC.
• LibreFM - A big collection of stations, with fully-free music. Licenses
  allow downloads and reuse.
• Musopen - A site dedicated to copyright-free (and culturally free)
  music. Various licenses, all copyright-free (varies by piece).
• Open Music Archive - Digitized out-of-copyright sound
  recordings. Public domain in the UK.
• Silverman Sound Studios' Music Tracks - A bunch of musical
  tracks. CC-BY-4.0.

Sound Effects

• Audioaugust - A collection of sound effects, originally used for a
  game. CC-BY-4.0.
• Freesound.org - A collection of CC-licensed sound effects. Various
  licenses, all CC.
• jsfxr - A tool like sfxr-sdl but in ECMAScript. Unlicense.
• Opsound - A collection of assorted sounds. CC-BY-SA-3.0.
• sfxr-sdl - A tool to generate sounds. Expat.
• SoundBible's Royalty-free section - A collection of CC or
  public-domain-licensed sounds. Various licenses, all CC or public domain.

Communities

Gamedev can be a lonely job, and it also can have a steep learning curve. These
communities are designed to assist you in terms of camaraderie, expert knowledge
and resources.

• /r/freeculture - Part of the Free Culture Reddit Community. A general
  free-culture-focused community.
• /r/FreeGaming - Part of the Free Culture Reddit Community. Designed
  specifically for discussion of free culture games.
• /r/freesoftware - A general free-software-focused community.
• /r/godot - A community for discussion and support in development with
  the Godot game engine.
• FreeGameDev Forums - A forum community for all things free-game-development-related.
• FreeGaming - A freepo.st community dedicated to free gaming.
• Libregamewiki - The free gaming encyclopedia.

Engines

These are full-blown game engines.

General

• AGS - Implemented in C++. Scripted using its own scripting
  language. Designed for adventure games. Artistic License 2.0.
• AlephOne - Implemented in C++. Designed for FPS games. GNU GPLv3
  or later.
• AnKi 3D - Implemented in C++. 3-clause BSD.
• Arianne - Implemented in Java. Includes a multiplayer game
  framework. GNU GPLv2 only.
• Azul3D - Implemented in Go. 3-clause BSD.
• Backbone - Implemented in ECMAScript. Expat.
• BananaBread - Implemented in ECMAScript. A port of Sauerbrauten. zlib.
• Blender Game Engine - Implemented in C++. Scripted using a GUI and
  Python. GNU GPLv2 or later.
• Castle Game Engine - Implemented in ObjectPascal. GNU LGPLv2 or later.
• Chili Source - Implemented in C++. Expat.
• Cocos2d - Implemented in Python. 3-clause BSD.
• Cocos2d-android - Implemented in Java. 3-clause BSD.
• Cocos2d-X - Implemented in C++. Has ECMAScript, Lua and C++ scripting. Expat.
• DarkPlaces - Implemented in C. GNU GPLv2 or later.
• delta3d - Implemented in C++. Also useful for
  simulations. GNU LGPLv2 or later.
• Doomsday - Implemented in C++. GNU GPLv2 or later.
• Duality - Implemented in C#. Expat.
• EasyRPG - Implemented in C++. Designed for JRPG-style
  games. GNU GPLv3 or later.
• ENIGMA - Implemented in C++. Has its own scripting language
  and GUI editor. GNU GPLv3 or later.
• FIFE - Implemented in C++. Has Python scripting. Designed for isometric
  games. GNU LGPLv3 or later.
• Fillwave - Implemented in C++. Has an easy graphics API. FreeBSD.
• Flambe - Implemented in Haxe. Designed for 2D games. Expat.
• FLARE - Implemented in C++. Designed for action RPGs. GNU GPLv3 or
  later.
• Fluxus - Implemented in C++. Designed for livecoding
  worlds. GNU GPLv2 or later.
• gamekit - Implemented in C++. Scripted using C++, Lua or logic blocks. Expat.
• GamePlay - Implemented in C++. Apache2.0.
• GDevelop - Implemented in C++. Targeted at non-programmers. Expat
  (IDE is GNU GPLv3 only.)
• GNU FreeDink - Implemented in C++. GNU GPLv3 or later.
• Godot - Implemented in C++. Has its own scripting language. Expat.
• Gosu - Implemented in C++. has a Ruby interface. Expat.
• Helm - Implemented in Haskell. Expat.
• HERITAGE - Implemented in ECMAScript. Designed for text adventure
  games. GNU GPLv3 or later.
• Horde3D - Implemented in C++. EPLv1.
• ioquake3 - Implemented in C. A fork of the Quake III Arena
  engine. GNU GPLv2 or later.
• Irrlicht - Implemented in C++. Has a range of bindings. zlib.
• JMonkey - Implemented in Java. 3-clause BSD.
• KivEnt - Implemented in Python. Expat.
• LambdaHack - Implemented in Haskell, Designed for roguelikes. 3-clause BSD.
• lycheejs - Implemented in ECMAScript. Designed for construction of HTML5
  or native SDL games. Expat.
• Maratis - Implemented in C++. Has Lua for scripting. GNU GPLv2 or
  later.
• Moai - Implemented in C++. Has Lua for scripting. CPAL.
• OctaForge - Implemented in C++. Has LuaJIT for scripting. Fork of
  Sauerbraten. NCSA Open Source License.
• Ogre3D - Implemented in C++. Has a range of bindings. Expat.
• Orx - Implented in C. zlib.
• Oxygine - Implemented in C++. Expat.
• Panda3D - Implemented in C++. Has a Python interface. 3-clause BSD.
• PlayN - Implemented in Java. Apache2.0.
• Processing - Implemented in Java. Has its own scripting
  language. GNU GPLv2 only.
• Processing.js - Implemented in ECMAScript. Has its own scripting
  language. Expat.
• qfusion - Implemented in C++. Designed for FPS games. GNU GPLv2
  or later.
• Ren'Py - Implemented in Python. Designed for visual
  novels. Expat, with some parts under GNU LGPLv3 only.
• SGE - Implemented in Python. Designed for 2-D games. GNU GPLv3
• SLUDGE - Implemented in C++. Has its own scripting
  language. GNU LGPLv3 only with the GTK Dev Kit GNU GPLv3 or later.
• Sly - Implemented in Guile. Uses functional reactive
  programming. GNU GPLv3 or later.
• Solarus - Implemented in C++. Comes with its own editor. Designed for
  RPGs. GNU GPLv3 or later.
• Spearmint - Implemented in C. Designed for FPS games. GNU GPLv3
  or later.
• Spring - Implemented in C++. Designed for RTS games. GNU GPLv2 or
  later.
• Torque2D - Implemented in C++. Has its own scripting language. Expat.
• Torque3D - Implemented in C++. Has its own scripting language. Expat.
• Turbulenz - Implemented in ECMAScript. Expat.
• Urho3D - Implemented in C++. Scripted using AngelScript or Lua. Expat.
• voxeliq - Implemented in C#. Designed for voxel world games. MsPL.

HTML5

Unless stated otherwise, these engines are implemented in ECMAScript.

• Akihabara - Designed for 8-bit and 16-bit games. Expat.
• Babylon.js - Apache2.0.
• Cocos2d-html5 - Expat.
• Coffee2D - Implemented in CoffeeScript. Expat.
• Crafty.js - Expat.
• Cube - Designed for voxel games. WTFPLv2.
• kiwi.js - Expat.
• melonJS - Expat.
• panda.js - Expat.
• Phaser - Expat.
• PlayCanvas - Expat.
• PuzzleScript - Expat.
• Superpowers - ISC.

Physics

• ammo.js - Implemented in ECMAScript. A port of Bullet. 3-clause BSD.
• Box2D - Implemented in C++. Designed to simulate rigid body physics. zlib.
• Bullet - Implemented in C++. General physics engine. zlib.
• LiquidFun - LiquidFun is a 2D rigid-body and fluid simulation C++ library for games based upon Box2D. zlib.
• Matter.js - Implemented in ECMAScript. Physics engine for HTML5. Expat.
• ODE - Open Dynamics Engine; implemented in C++. Designed to simulate
  rigid body dynamics. Original BSD.
• Oimo.js - Implemented in ECMAScript. Expat.
• Physics.js - Implemented in ECMAScript. Expat.

Fonts

• Google Fonts - A collection of freely-licensed fonts. OFL.
• Open Font Library - A collection of freely licensed fonts. OFL.
• ParaType Public Fonts for Minority Languages of Russia - Three
  freely-licensed fonts with support for many character
  sets. ParaType Free Font Licensing Agreement.
• The League of Moveable Type - A collection of fonts with high
  standards. OFL.

Games

These are meant to serve as examples for your own work, or foundations to built upon.

I have endeavoured to provide both code and asset licenses here - if no asset
license is listed, assume it to be non-free or questionably-free. These entries
may be removed upon clarification.

C

• 2048-cli - A CLI version of 2048. Expat (code), no significant assets.
• 2048-in-terminal - A CLI version of 2048. Expat (code), no
  significant assets.
• Craft - A 3D voxel world game. Expat (code and assets).
• Curse of War - A fast-paced strategy game. GNU GPLv3 or later
  (code and assets).
• The Legend of Edgar - A 2D platform game with a persistent
  world. GNU GPLv2 or later (code), various free culture licenses
  (assets).
• FallingTime - An arcade game. GNU GPLv2 or later (code),
  various CC (no NC or ND) (assets).
• Taisei - Expat (code and assets), OFL only for one font.
• Turtle Arena - Third-person action game. GNU GPLv3 or later
  (code), various free culture licenses (assets).
• Wizznic - A puzzle game. GNU GPLv3 or later (code and assets).

C++

• Battle for Wesnoth - A turn-based strategy game. GNU GPLv2 or
  later (code and assets).
• Blackvoxel - A voxel exploration and crafting game. GNU GPLv3
  or later (code and assets).
• Clonepoint - GNU GPLv3 or later (code), various CC (no NC or
  ND) (assets).
• colobot - A robot-based strategy game. GNU GPLv3 or later (code
  and assets).
• Egooboo - A 3D dungeon crawler in the spirit of
  NetHack. GNU GPLv3 or later(code and assets).
• Endless Sky - 3D space exploration game. GNU GPLv3 or later
  (code), various CC (no NC or ND) (assets).
• Freeminer - A 3D voxel world game. GNU GPLv3 or later
  (code), CC-BY-SA-3.0 (assets).
• MegaGlest - A 3D RTS game. GNU GPLv3 or later
  (code), CC-BY-SA-3.0 (assets).
• Minetest - A 3D voxel world game. GNU LGPLv2 or later
  (code), CC-BY-SA-3.0 (assets).
• Minilens - A cute puzzle platformer starring a cleaning robot on
  post-Apocalyptic Earth. Made with the Godot engine. GNU GPLv3 or later
  (code), CC-BY-SA-3.0 (assets).
• Monster 1 - A JRPG-style game. 3-clause BSD (code and assets).
• Monster 2 - A JRPG-style game. zlib (code and assets).
• OpenClonk - A jump'n'run/settlement/combat game. ISC (code),
  CC-BY-SA-3.0 at most but mostly CC-BY-3.0 (assets).
• OpenDungeons - A version of Dungeon Keeper. GNU GPLv3 or later
  (code), various free culture licenses (assets).
• Return of Dr. Destructo - An adventure game. Expat (code),
  CC-BY-SA-4.0 (assets).
• SavageWheels - A car game. Expat (code and assets).
• Seven Kingdoms: Ancient Adversaries - A strategy
  game. GNU GPLv2 or later (code and assets).
• SuperTux - A platformer. GNU GPLv3 or later (code), various
  free culture licenses (assets).
• SuperTuxKart - A 3D racing game. GNU GPLv3 or later (code),
  various free licenses (assets).
  (code), CC-BY-SA-4.0 (assets).
• The Powder Toy - A sandbox falling sand physics game. GNU GPLv3
  or later (code and assets).
• Übergame - A multiplayer, casual FPS game. Expat
  (code), CC0 (assets).
• Warzone 2100 - An RTS sci-fi game. GNU GPLv2 or later (code),
  various free culture licenses (assets).

CoffeeScript

• coffee-snake - A version of Snake. GNU GPLv3 or later (code),
  no significant assets.
• Zop - A 'connect the dots' game. Expat (code), no significant assets.

Dart

• Hauberk - A roguelike. Expat (code), no significant assets.
• Pop, Pop, Win! - A version of Minesweeper. 3-clause BSD (code
  and assets).

ECMAScript

• 2048 - The original, classic casual game. Expat (code and assets).
• A Dark Room - A text adventure game. MPLv2 (code), no
  significant assets.
• Blockrain.js - A version of Tetris. Expat (code and assets).
• BrowserQuest - An MMORPG. MPLv2 (code), CC-BY-SA-3.0 (assets).
• Clumsy Bird - A version of Flappy Bird. Expat (code and assets).
• Drunken Viking - A top-down puzzle game. Expat (code), various
  CC (no NC or ND) (assets).
• Freeciv-web - A port of Freeciv. GNU GPLv2 or later
  and GNU AGPLv3 or later (code and assets).
• ludum-dare-28 - CC-BY-4.0 (code and assets).
• Masonry-JavaScript-Tetris-Clone - Exactly what it says on the
  tin. Expat (code and assets).
• Parity - Expat (code), no significant assets.
• Particle Clicker - An incremental game that teaches the history of
  high-energy particle physics. Expat (code and assets).
• Prism - A colour-matching game. Expat (code), no significant assets.
• Roguish - A roguelike. 3-clause BSD (code and assets).
• Snake - A version of Snake. Expat (code), no significant assets.
• Sorades 13k - A scrolling shooter. CC-BY-SA-3.0 (code and assets).
• Space Crusade - A space game. Expat (code), CC0 (assets).
• Space Shooter - Simple space shooting game. Expat (code).
• Squirts - Expat (code and assets).

Java

• epic-inventor - An indie, side-scrolling RPG. GNU GPLv2 only
  (code and assets).
• Ned et les maki - A 3D puzzle game. Expat
  (code), FALv1.3 (assets).
• Newton Adventure - A puzzle game. 3-clause BSD (code), various
  CC (no NC or ND) (assets).
• PuzzleGame - A slider puzzle game. Uses Android port of Cocos2D
  engine. Expat (code and assets).
• Terasology - A 3D voxel world game. Apache2.0 (code and assets).

Other/Multiple

• Cataclysm: Dark Days Ahead - A roguelike set in a post-apocalyptic
  world. CC-BY-3.0 (code), CC-BY-SA-3.0 (assets).
• DynaDungeons - A version of Bomberman. Uses Godot
  engine. GNU GPLv3 or later (code), various CC (no NC or ND) (assets).
• FLARE - A dark fantasy 2D RPG. Uses FLARE engine. GNU GPLv3 or
  later (code), CC-BY-SA-3.0 (assets).
• Pioneer - A space exploration game. Implemented in C++ and
  Lua. GNU GPLv3 only (code), CC-BY-SA-3.0 (assets).
• Source of Tales - An MMORPG. Scripted using Lua (implementation
  language unclear). GNU GPLv3 or later (code), CC-BY-SA-3.0
  and GNU GPLv3 (assets).
• Tanks of Freedom - Pixed-based turn-based strategy. Uses Godot
  engine. Expat (code and assets).
• Teeworlds - Implemented in C and C++. 3-clause BSD
  (code), CC-BY-SA-3.0 (assets).
• Zero-K - An RTS game. Uses Spring engine. GNU GPLv2 or later
  (code and assets).

Python

• Bullet dodger - A fun and challenging mouse game where you must dodge
  bullets. GNU GPLv3 only (code), various CC (no NC or ND) (assets).
• Hexoshi - Free-roaming Metroid-like. GNU GPLv3 only (code),
  various CC (no NC or ND) (assets).
• Mystic Mine - Expat (code and assets).
• ReTux - A platformer. GNU GPLv3 only (code), various free
  culture licenses (assets).
• RogueBox Adventures - A mix of classical roguelike and sandbox
  game. GNU GPLv3 or later (code), various free culture licenses (assets).
• Unknown Horizons - A real-time strategy simulation
  game. GNU GPLv2 or later (code), CC-BY-SA-3.0 (assets).

Graphics

Assorted

This is a section for everything else that doesn't fit in some other graphics category.

• Blender 3D Model Repository - User-submitted 3D models made with
  Blender. Various licenses, including free ones.
• Blend Swap - A community of Blender artists and their work. Various
  licenses, all CC.
• CanTree - Free online tree generator. Generates PNG files. Expat.
• Kator Legaz 3D Models - 3D Models by of various
  subjects. CC-BY-3.0.
• mocapdata.com - A library of motion capture data. Various licenses,
  including free ones.
• Yobi3D - A search engine for 3D models that aims to display license
  information when possible. Various licenses, including free ones.

Collections

This category contains any 'grab-bags' of different kinds of art assets.

• Free stuff by 7Soul1 - A collection of various game-related
  assets. Available in PNG. Public domain.
• openclipart - A collection of various clip art. Available in PNG. Public domain.
• Remastered Tyrian graphics - A collection of pixel spreadsheets for a
  top-down shooter. CC0.
• Vecteezy - A collection of vector art. Various Creative Commons licenses.
• ZipUp Free Game Elements - A collection of various graphical
  elements. Custom attribution license, free.

Icons

• FatCow - A set of 3900 colour icons in 16x16 and 32x32 pixel format. CC-BY-3.0.
• Font Awesome - A large set of vector icons. CC-BY-4.0.
• Game-icons.net - A constantly-growing collection of black-and-white
  icons. Available in SVG or PNG. CC-BY-3.0.
• IconFontCppHeaders - C and C++ headers for icon fonts Font Awesome, Material Design Icons and Kenney Game Icons. zlib
• Kenney Game Icons - A font pack specifically designed for (browser) games and other gaming related websites/projects. CC0.
• Material Design Icons - An official icon set from Google following
  specific guidelines. CC-BY-4.0.
• Tango Icon Library - An icon set project with a goal to create a
  consistent user interface. Public domain.

Sprites

• LPC Spritesheet Character Generator - A pixel-art RPG-style character spritesheet generator. Arts are dual licensed : GNU GPLv3 and CC-BY-SA3
• SpriteLib - A big collection of sprites. Available in PNG. CPL 1.0.

Graphics Tools

Animation

• Synfig Studio - A 2D animation tool. GNU GPLv2 or later.

Bitmap Compression

• FLIF - Reference implementation of the Free Lossless Image
  Format. Comes with additional tools. GNU GPLv3 only.
• pngquant - A command-line utility for lossy compression of PNG
  images. Has various front-ends available. FreeBSD.
• Trimage - A cross-platform tool for losslessly optimizing PNG and JPG
  files. Expat.

Editors

• AwesomeBump - A program that generates normal, height, specular or
  ambient occlusion, roughness or metallic textures. Requires a graphics card
  with support for OpenGL4 or greater. GNU LGPLv3 or later.
• Blender - A 3D modelling and rendering editor. GNU GPLv2 or later.
• GIMP - The GNU Image Manipulation Program. Designed for photo
  retouching, image composition and similar tasks. GNU GPLv3 or later.
• GrafX2 - A bitmap paint program specialized for 256-color
  drawing. GNU GPLv2 only.
• Hme - A program for creating, manipulating and viewing height
  maps. GNU GPLv2 or later.
• Inkscape - A vector image editing program. GNU GPLv2 only.
• Krita - A digital painting and illustration program. GNU GPLv2 or
  later.
• MakeHuman - A tool for making 3D characters. GNU AGPLv3 or later.
• MyPaint - A natural materials painting and drawing
  emulator. GNU GPLv2 or later.
• NeoTextureEdit - An easy-to-use, graph-based, procedural texture editor.
  GNU LGPLv3 or later.
• ngPlant - A 3D plant modelling software suite. GNU GPLv2 or later.
• NormalMapOnline - An online normal-mapping tool. Expat.
• Overlap2D - An engine-agnostic game level and UI editor. Apache2.0.
• Synfig Studio - 2D animation software. GNU GPLv2 or later.
• Tiled - Easy-to-use and flexible tile map editor. GNU GPLv2 or
  later and FreeBSD.

Mesh Tools

• MeshLabs - A portable system for the processing and editing of
  unstructured 3D triangular meshes. GNU GPLv2 or later.
• Dilay - A 3D sculpting application that provides an intuitive workflow
  using a number of powerful modelling tools. GNU GPLv3 or later.

Procedural Generators

• SpaceshipGenerator - A Blender script allowing generation of spaceships
  from a random seed and some parameters. Expat.

Spritesheet Tools

• Piskel - Online pixel art and animated sprite creator. GNU AGPLv3
  or later.

Texture Tools

• TextureGeneratorOnline - An online tool for texture generation. Expat.

Voxel Editors

• Sproxel - A 3D interface for quickly editing and creating voxel-based 3D
  models. 3-clause BSD.

Learning Resources

These are all collections of information to help you learn about things that
might be necessary for developing games.

We aim for complete and current resources here whenever possible.

Game Design

• School of Game Design, Wikiversity - A collection of learning resources
  for would-be game designers. CC-BY-SA-3.0.

Graphics

Beginner

• Blender 3D: Noob to Pro - A Wikibook for learning how to make 3D
  graphics with Blender. CC-BY-SA-3.0.

Reference

• Procedural Content Generation Wiki - A collection of articles about the
  use of procedural generation to make stuff in games. CC-BY-SA-3.0.

Music

• LibreMusicProduction - A community-driven online resource for
  promoting musical creation and composition using free
  tools. CC-BY-SA-4.0.

Programming

• Computer Science section on Saylor Academy - A collection of computer
  science courses. Many of these deal with useful concepts for game
  programming. CC-BY-3.0.
• Introduction to Mobile Game Development - Class on making simple mobile
  games with Gideros and Lua. Expat.

Beginner

• An Introduction to Python - Pretty much what it says on the
  tin. Python License.
• Beginner 2d Game Programming Tutorial (video) - A set of tutorials in
  2D game programming, illustrated using ECMAScript. CC-BY-3.0.
• C++ Tutorial for Beginners (video) - A collection of basic video
  tutorials for C++. CC-BY-3.0.
• Effective Go - A guide to writing good, clean and readable Go code for
  beginners. CC-BY-3.0 (text), 3-clause BSD (code).
• Functional Programming in JavaScript (video) - A series of tutorials
  about functional programming concepts, illustrated using
  ECMAScript. CC-BY-3.0.
• Java Collections Framework (video) - A set of tutorials for using Java
  collections properly. CC-BY-3.0.
• Java For Complete Beginners (video) - A collection of basic video
  tutorials for Java. CC-BY-3.0.
• Lua Programming - A completed Wikibook on programming Lua. CC-BY-SA-3.0.
• Practical Haskell - getting started with Stack - A series of tutorials
  designed to help people get started programming Haskell. CC-BY-SA-4.0.
• pygame_stuff - A collection of code samples using
  PyGame. GNU GPLv3 or later.
• The GNU C Programming Tutorial - An introduction to programming in C by
  the nice GNU people. PDF. GNU FDL.
• why's (poignant) Guide to Ruby - An interesting introductory book for
  Ruby. CC-BY-SA-3.0.

Intermediate

• Advanced C++ (video) - A tutorial on advanced aspects of C++. CC-BY-3.0.
• Dive Into Python - A Python book for experienced programmers. GNU FDL.
• Haskell - A very thorough Wikibook on programming Haskell. CC-BY-SA-3.0.
• Haskell Tutorial for C Programmers - An introduction to Haskell for
  people coming from C-family languages. Expat.
• JavaFX Tutorial (video) - A series of videos about how to use JavaFX to
  make GUIs. CC-BY-3.0.
• Java Multithreading (video) - A series of videos about how to do
  multithreading work in Java. CC-BY-3.0.
• Mostly adequate guide to functional programming (in JavaScript) - A
  book on the fundamentals of functional programming in
  ECMAScript. CC-BY-SA-4.0.
• Structure and Interpretation of Computer Programs - A classic
  programming and teaching text. Designed for teaching Scheme, but can be useful
  to anyone writing in any language. CC-BY-SA-4.0.

Reference

• breakouts - A collection of ECMAScript implementations of
  Breakout. Expat.
• Haskell Programming - A complete wiki of the Haskell programming
  language. Expat.
• Joey Hess' blog - A collection of posts, many of which are about
  Haskell use. CC-BY-4.0.

Talks

These are collections of game development-related talks, podcasts etc. that
might be interesting or informative to people seeking to design games.

• GameDevRadio (podcast) - A series of online radio shows devoted to
  entertaining and educating whoever is interested in game
  development. CC-BY-SA-4.0.
• Indievelopment talks (video) - A collection of talks about various
  aspects of game development. CC0.

Programming Frameworks and Libraries

These are programming libraries or low-level code-based tools which are designed
to support game programming, but do not provide as much structure or support as
an engine would.

• ActionKid - A simple video game framework. Implemented in
  Haskell. 3-clause BSD.
• Allegro 5 - A cross-platform library for low-level tasks, like creating
  windows, accepting user input and so forth. Implemented in C and
  C++. 3-clause BSD.
• Bacon2D - A framework to ease 2D game development, providing QML
  elements representing basic game entities. Implemented in C++. Expat.
• bgfx - A 'build-your-own-engine' rendering library. FreeBSD.
• Chipmunk2D - A fast and lightweight 2D game physics library. Implemented
  in C. Expat.
• ChipmunkSharp - Advanced physics engine library based on
  Chipmunk. Implemented in C#. Expat.
• Cinder - A community-developed library for creative
  coding. Implemented in C++. FreeBSD.
• ClanLib - A cross-platform toolkit with a primary focus on game
  creation. Implemented in C++. ClanLib license.
• CutJS - A lightweight and fast 2D HTML5 rendering engine for
  cross-platform game development. Implemented in ECMAScript. Expat.
• Dear ImGui - An Immediate Mode Graphical User interface for C++ with minimal dependencies. zlib
• enchant.js - A framework for developing simple HTML5 + ECMAScript
  games. Implemented in ECMAScript. Expat.
• EndGate - A framework for building HTML5 games. Implemented in
  TypeScript. Expat.
• Epoxy - A library for handling OpenGL function pointer
  management. Implemented in C. Expat.
• GameJs - A thin library on top of the Canvas API, including some
  helpful game development modules. Expat.
• Gideros - A cross-platform game development framework in Lua. Various
  licenses, all free.
• Gladiator3D - A raycasting engine. Implemented in
  ECMAScript. Expat.
• GLFW - A multi-platform library for OpenGL, OpenGL ES and Vulkan development on the desktop. zlib
• HaxeFlixel - A cross-platform development framework, supporting many
  targets. Implemented in Haxe. Expat.
• HaxePunk - A development framework designed to let you build games on
  any platform. Expat.
• ImGuizmo - An immediate mode 3D gizmo for scene editing and other controls based on Dear ImGui. MIT
• Kivy - Rapid-development library for multi-touch and visual apps on many
  platforms. Implemented in Python. Expat.
• Kuko - A cross-platform development library, designed for mobile
  devices. Implemented in C++ and Lua. Expat.
• libGDX - Cross-platform game development framework. Implemented in
  Java. Apache 2.0.
• libRocket - An HTML/CSS-based UI library. Implemented in
  C++. Expat.
• libSDL2pp - A set of C++11 bindings for SDL2. Implemented in
  C++. zlib.
• LimeJS - A framework for building fast HTML5 games. Implemented in
  ECMAScript. Apache 2.0.
• LoomSDK - A very large and powerful framework for cross-platform 2D
  game development. Implemented in C++. Apache 2.0.
• LÖVE - A framework for making 2D games. Implemented in Lua. zlib
  .
• MINX - MINX Is Not XNA; a framework resembling XNA. Implemented in
  C++. 3-clause BSD.
• p2.js - 2D physics library. Implemented in ECMAScript. Expat.
• pixi.js - A 2D rendering engine. Implemented in
  ECMAScript. Expat.
• Polycode - Framework for games and interactive
  applications. Implemented in C++. Has Lua bindings. Expat.
• PyDark - Game framework on top of PyGame; designed to be easy to pick
  up. Implemented in Python. Expat.
• PyGame - A set of modules designed for writing games. Implemented in
  Python. GNU LGPLv2 or later.
• Quasi-Engine - A set of Qt-based tools for game
  development. Implemented in C++. GNU LGPLv2 or later.
• raylib - Low-level library designed to learn videogames programming.
  Implemented in C, but has Lua and Go bindings. zlib
• SDL - Another cross-platform library for low-level tasks, like creating
  windows, accepting user input, and so forth. Implemented in C. zlib.
• SFML - Simple and Fast Multimedia Library; a multi-platform,
  multi-language, multimedia interface to various computer hardware. Implemented
  in C++. Has a range of bindings. 3-clause BSD.
• Slick2D - A set of tools to make 2D game development
  easier. Implemented in Java. 3-clause BSD.
• Three.js - A library that makes WebGL easy to use. Implemented in
  ECMAScript. Expat.
• voxel.js - A multi-component framework for bulding voxel games for
  modern browsers. Implemented in ECMAScript. 3-clause BSD.
• ZenGL - A cross-platform game development library designed to provide
  necessary functionality for rendering 2D-graphics, handling input, sound output,
  etc. Implemented in Pascal. zlib.

Utilities

This is a catch-all category for things that don't fit anywhere else.

• Assimp - Open Asset Import Library; a portable way to import various
  well-known 3D model formats in a uniform manner. Implemented in C++, with a
  range of bindings. 3-clause BSD.
• Easel.js - Provides a range of tools to make working with the HTML5
  Canvas API easier. Implemented in ECMAScript. Expat.
• Gmsh - A 3D finite-element grid generator with a built-in CAD engine
  and post-processor. GNU GPLv2 or later.
• libcaca - An ASCII graphics rendering library for terminal-based
  interfaces. WTFPLv2.
• libnoise - A portable coherent noise-generation library. Implemented
  in C++. GNU LGPLv2 or later.
• PhysicsFS - A library to provide abstract access to various
  archives. zlib.
• ScummVM - A program which allows you to run certain classic graphical
  point-and-click adventure games, provided you already have their data
  files. GNU GPLv2 or later.
• Torsion - A TorqueScript IDE. Expat.
• TrenchBroom - A cross-platform level editor for Quake-engine-based
  games. Currently supports Quake, Quake 2 and Hexen 2 engine-based
  games. GNU GPLv3 or later.
• WorldForge - Provides everything needed to create your own free
  software MMORPG. GNU GPLv3 or later (or a compatible license).