The overview includes only games which are completely free, with a permissive license for both the code and their content. I could not include here games like Urban Terror or Warsow, since their assets are not free, nor Steam games.
0 A.D. is a strategy game that has been around for quite some time now, and it reached a decent level of completeness despite the fact that Wildfire Games are releasing only alpha versions.
* 0 AD is a historical real-time strategy open-source game.
* Red Eclipse is a single-player and multi-player first-person ego-shooter, built as a total conversion of Cube Engine 2, which lends itself toward a balanced gameplay, with a general theme of agility in a variety of environments
0 A.D. is an open-source, 3D real time strategy game with an ancient warfare theme, developed by Wildfire Games, and using the Pyrogenesis engine.