Spring is a free RTS engine developed for Windows, Linux and Mac OS X.
2D ARPG Engine
Open Game Bootstrap
Mahasona engine is an open source game engine.
Create 2D mini-game easily with this lib
Multimedia asset management and manipulator for Étoilé
Multi-threaded 2D Renderer licensed under the Mozilla Public License
C++ Framework for slot machine games
Kinect based controller.
Simple Point & Click Game
Tween for Torque
A 2D Java game engine