A modern, cross-platform Quake game engine based on FitzQuake.
Game engine supporting many 3D/2D formats and graphic effects
A free 3D game engine to create games and realtimes scenes for Windows
C++ lightweight cross-platform game engine
Pycraft is an open-source, OpenGL based game made in Python
Vivid3D is an open-source 3D engine with powerful 2D UI.
Spring is a free RTS engine developed for Windows, Linux and Mac OS X.
DOOM / Heretic / Hexen source port with enhanced graphics and UI
A 2D game engine and level editor
A 3D game engine in java.
2d/3d Game Engine
A basic 3D environment with a first-person POV
3D Game engine
Visual Novel engine, editor and game development.
3D game engine for C and C++