ID has released the source code to idtech1-3 and it has done wonderful things for the open source company. Take a look at warsow, which is based on the idtech2

ID has released the source code to idtech1-3 and it has done wonderful things for the open source company. Take a look at warsow, which is based on the idtech2 engine (engine used for quake II): http://www.warsow.net/ http://www.warsow.net/ There are also a variety of games using idtech3 (quake 3 engine) such as UrbanTerror, OpenArena, and Nexuiz (http://www.urbanterror.info/home/ http://www.urbanterror.info/home/ http://openarena.ws/smfnews.php http://openarena.ws/smfnews.php http://www.nexuiz.com/ http://www.nexuiz.com/). I'm not sure idtech4 is as suited for fast multiplayer gaming like the idtech2/3 engines were, but who knows what the open source community will come up with.