I checked out a pretty cool game called Tremulous. Its a free and open source, team-based first person shooter. The game features two teams, humans and aliens, and the aim is to build and protect a base. I am not sure I quite got the hang of it, I managed to shoot and kill Jack, who happened to be on my team….oops.
Tremulous is licensed under the GPL, although it includes code from other projects that was released under other GPL-compatible licenses. Most of the game media is licensed under the Creative Commons Attribution-ShareAlike 2.5 License.
The release of the game as free and open source software has meant that programmers can modify the game and game engine. This has meant that a growing number of players are releasing patches for the game in order to remove bugs, add features to the game or modify the game play itself.
Its well worth a look. I am going to need a bit more practice I think.