scene-oriented, flexible 3D engine (C++, Python, C#, Java)
... the open-source glide computer
GemRB is a portable open-source implementation of the Infinity Engine
PyMancala: A Python API for the Mancala game
Urho3D Game engine
The AWS GameKit Plugin for Unreal
ZED OS the clone of Windows XP
2D Game Engine
Character animation system for games and simulations.