Here's a curious project that looks interesting! It's called Q3min, and promises "small but fully functional clone of Quake III Arena".
See
http://q3min.org/forum/docs/q3min_manifest.html and
http://q3min.orgManifest states that it does borrow from ioquake3 as well as from Openarena.
I have yet to try to use Q3min on a non-pure Openarena server