Free Dedicated Server.
It is played by many... It's a great multiplayer game. The best.
As for mod community... I just recently (this Saturday) hosted, on GameSpy Arcade a chat session with the mod team of C&C Reborn, a modification for Renegade to bring the Tiberian Sun theme to the game... With mechs, drones, AI troopers from drop-pods and all in multiplayer. You can check out the full chat log and links to screens and videos at
http://www.planetcnc.com/community/rebornOr check out the official website of this mod at
http://www.planetcnc.com/ammo/rebornI'm planning on hosting another chat session on GameSpy Arcade in just over 2 weeks with the mod team of Renegade Alert, a team that is making a TC of Renegade to Red Alert (the original), it's another great modification.
Some of the other mods in development include a StarCraft based modification, a WW2 based modification, a GI Joe based modification and many others.