There is another project as a alternative to Openarena, called Q3Min (Minimal) based on the free and advanced ioQuake 3 engine.

The goal is to released all content under GPL, and of course for free, except the maps. Check the Q3Min Hompage and their forum.

"This is a community project managed by dedicated Quake III Arena enthusiasts. Its purpose is to provide a freely distributable minimal version of Q3A that is fully compatible with the original game created by id Software. We wish to make a package that can use different mods as well as custom maps made for the original game Q3A. The package should have a reasonably small size for easy downloading.

We do not intend to stop when the first fully functional package is released. We would like to implement, test and maybe permanently integrate different enhancements suggested by people on Q3A forums. We want to make a game even better than the original!"
Background (dont know if its true)
It seems the background is a conflict with the chief from Openarena, Leilol. A team did 80% of new textures for Openarena but it wasnt Leilol not enough GPL´ed, so this team is now working on their own Quake 3 Version.

You can download the dm-maps seperatly, and rename all the .zip to .pk3 in a directory with the dos command "ren *.zip *.pk3"

GL & HF to Q3Min