Open source clone of the Age of Empires II engine
GemRB is a portable open-source implementation of the Infinity Engine
A retro game engine for Python
Free, open source game engine online
3D game engine/framework in C, with Luajit and Python bindings now
Powerful, mature open-source cross-platform game engine for Python
scene-oriented, flexible 3D engine (C++, Python, C#, Java)
Pycraft is an open-source, OpenGL based game made in Python
A game engine for console based text games
DOOM / Heretic / Hexen source port with enhanced graphics and UI
Python ctypes module for the Irrlicht Engine SDK
KlayGE is a cross-platform open source game engine
The second demo of my game engine.
Text Based Game Engine and Parser
Open source, moddable game engine for the "Polygon Love 2" game
Tactical, turn-based game engine, that uses OpenGL and WinAPI
Scripting language of the hawk game engine
Browser game engine