Quake III Arena GPL Source Release
Open-Awesome is built by the community, for the community. Submit a project, suggest an awesome list, or help improve the catalog on GitHub.
DOOM Open Source Release
Open Source real-time strategy game engine for early Westwood games such as Command & Conquer: Red Alert written in C# using SDL and OpenGL. Runs on Windows, Linux, *BSD and Mac OS X.
OpenTTD is an open source simulation game based upon Transport Tycoon Deluxe
The source code to VVVVVV! http://thelettervsixtim.es/