As you can see, with some modification the icculus.org quake 3 sources and running the system via software ( running the app with ./ioquake3.ppc64 "+set r_allowSoftwareGL 1" )
There are a few modules and dependancies which you'll need to install to get this up and running, mainly openAL and openAL-devel, but i i'll assume you know what you're doing enough to get things going yourself.
What you need to do is su then,
1. svn co svn://svn.icculus.org/quake3/trunk quake3
2. cd quake3
3. ./configure
4. make
Make may fail if you have not installed the openAL/openAL-devel libs, so get them sorted out BEFORE you do

Naoneo has also created a brief video demonstrating the startup process of the game and a short amount of gameplay. When in-game, it is noticed that the game is not running at full speed, and that there are speed restrictions on this right now. One of the only solutions to this slow game speed issue is Sony themselves allowing hardware acceleration of their graphic chipsets. However, it's still playable to an extent, and you can judge for yourself by watching the video.