Mob2D is a 2D rendering engine designed from the ground up to provide simplicity above all else while still being robust and flexible. You could make a 2D game with this engine with only relatively little knowledge of OpenGL.
The Beholder project was begun with the purpose of creating an open source code library for use in cross-platform development of game software based on the D20 Game License released under the OGL by Wizards of the Coast.
BTS is a Build Template System designed for building packages for th common packing systems in use by current distributions based on a single XML package description. We are finally restarting development after a long break due to NeOS work.