Excessive dawn (edawn) is a free Quake 3 Arena mod, with numerous improvements, both client and server side. Biggest feature is the fact you can tweak almost every single aspect of the game, from weapon behaviour to making your own mini gametypes. All powered by a tweaked netcode. Mod works with any Quake 3 version that uses QVM (quake virtual machine): vanilla Q3 Arena, open arena, ioquake3, whatever executable you might make yourselves..
This is a community made 1.32e patch, wich is the mod based on. Supports newer windows and has some bugfixes.