Open Source Gaming

[NimbleJack3]

I have noticed that there are some fairly good-quality games out there that are open surce.
Now for those of you who don't know, open source software is software that is distributed freely and without charge, with all the data (or source code) open for you to browse and change it all you like. The only catch is that if you make a change and want to give it to the masses, you must give it away for free too and credit any previous authors.
I have seen some wonderful quake-clones out there like OpenArena and Nexuiz, and these are avadible on almost any computer operating system. Has anyone else found any open-source gaming gems?

 

[Veylon]

TA Spring. After Cavedog bit the dust, some fans made a fully 3D remake. It now has LUA scripting, easily customizable GUI, fully interchangeable mods. And there's a server to play online with others. If you're into RTS, check it out.

 

[Kstreitenfeld]

TA Spring. After Cavedog bit the dust, some fans made a fully 3D remake. It now has LUA scripting, easily customizable GUI, fully interchangeable mods. And there's a server to play online with others. If you're into RTS, check it out.

Oh man, I need to check this out.

 

[NimbleJack3]

Looks good, thanks for the direction. Looks like Supreme Commander.