UCI chess engine
A simple and easy-to-use library to enjoy videogames programming
Desktop/Android/HTML5/iOS Java game development framework
One framework for creating powerful cross-platform games
The source code to VVVVVV
Urho3D Game engine
scene-oriented, flexible 3D engine (C++, Python, C#, Java)
New Godot bindings for Swift
3D modeler, 3D game maker, 3D demo maker
Orx: Portable Game Engine
Children's learning programming language Karel the Robot in 3D
Open-DIS implements the IEEE DIS protocol in multiple languages.
3D .NET engine for Windows, Linux, Mac
2D physics engine for games
A cross-platform OpenGL based lightweight scenegraph library
Cross-platform 2D game engine