A dead simple 2D game engine for Go
GemRB is a portable open-source implementation of the Infinity Engine
Orx: Portable Game Engine
Zoomable user interface (ZUI) with file manager, file viewers and more
Game engine supporting many 3D/2D formats and graphic effects
Character animation system for games and simulations.
3D .NET engine for Windows, Linux, Mac
plugin-based RPG manager in C++ and Qt5
Kids Games in Flash
Android/Flash educational children's games