Announced today on the ioquake3 blog is a call for all content creators. The baseio game they want to do is a small game using the ioquake3 engine with Creative Commons licensed content. They're already working on CC-licensed textures, weapon models, player model, etc. Animators and mapping is what needs to be done the most right now and so they're hoping some artists within the community can help. Aside from the CC-nc-by-sharealike content, the ioquake3 will obviously remain under the GPL.
This Wiki page yields some additional details on the baseio ambitions. It seems like it will be another ioquake3-shooter with the only real difference to some of the other open-source games is that the game content is all under the Creative Commons. In fact, they seem to be taking some game assets from OpenArena for a starting point... It's too bad it doesn't look like they're really aiming for a unique gaming experience or anything to separate baseio from all of the other Linux/open-source first person shooters out there. It would have also been more interesting to see this as a game built atop the iodoom3 (open-source id Tech 4 engine) as right now there isn't much to show for there with that newer game engine.