ioquake3.org is the de-facto standard in Quake 3 technology post-opensource release. Others base themselves on the hard work of the hundreds who have contributed to ioquake3. Tremulous, World of Padman, Urban Terror. All use ioquake3.org for many reasons.
To hell if I EVER heard of a more broken, I say, BROKEN game! They took what was the best of Quake 3 and Broke it in every detail! Corrupting save files, overpowered enemies, dying instantly with full health and armor, frag skipping... IT IS A TOTAL MESS!!!