As promised, the Quake 3 mod Reaction Quake 3 has been released. This mod recreates the gameplay and levels from Action Quake 2, and offers some new levels of it's own as well. The download page has several mirrors listed, for the Windows, Linux and Mac builds. It's a 68mb download

Beta 1 Features:

All the Original Weapons and Items
Remember how it felt when you snuck behind a camper and launched the poor sucker across the map with the handcannon? Or remember the time you sniped the ears (and head) off the bunny-hopping auto-monkey? We do, and your MK23 pistol and all its friends have been faithfully re-created and await your return.

New and Ported Maps
Battle through new maps like the torn grounds of Chill and the shops of Reaction Mall. Return to the slimy confines of Sludge Inc. or the lush climate of Deep Canyon 2. Action happens everywhere.

Action Combat System
Aim is just as important in Reaction. Running and gunning makes for bad shots, while crouching and holding ground will get you more accuracy. Shoot someone in the legs and cripple him or her. A head shot is almost certainly fatal. Projectile wounds will bleed you to death unless time is spent to bandage yourself. All this adds up to another gameplay element that made Action what it was and what Reaction will be. ...