3D Scene Builder
Fork of AbuseSDL to carry on development
a UCI chess engine
Spring is a free RTS engine developed for Windows, Linux and Mac OS X.
Vivid is a modern C++ 3D engine using OpenGL4+
DOOM / Heretic / Hexen source port with enhanced graphics and UI
RTSish Game Engine
2D Game Engine
Improved version of the X-Ray Engine, the game engine
3D Game engine with editor
mGSTEP port of the Cube game engine
KlayGE is a cross-platform open source game engine
A 2D game engine and level editor
A cross-platform 2D game engine
IGS Labs
A cross platform Lua based game engine
A fast, scalable, distributed game server engine/framework for C++
Cross-platform 2D and 3D game engine
Opensource Game Studio
Free and Open Game Programming Language for Windows and GNU/Linux
Blueshift is a cross-platform 3D game engine implemented in C++