Open source clone of the Age of Empires II engine
A retro game engine for Python
scene-oriented, flexible 3D engine (C++, Python, C#, Java)
Game engine supporting many 3D/2D formats and graphic effects
PyCAPGE - Python Classic Adventure Point and Click Game Engine
A game engine for console based text games
DOOM / Heretic / Hexen source port with enhanced graphics and UI
Text Based Game Engine and Parser
Open source, moddable game engine for the "Polygon Love 2" game