To give you a little more information:
The Singleplayer of this mod is released, and able to downloaded here
. You can play this game for free and without UT3. So while you are waiting, you can enjoy yourself with this singleplayer campaign.
As for the multiplayer, we are waiting for an official release. It will be free download, just as the singleplayer, on release. So from that moment, UT3 is no more needed to play this game.
I expect (and pray) that the game will be released somewhere this year, and I really hope this summer! But there are no official release dates for this yet so yeah, being patient is the only thing we can do atm....
And as nzdriver said, the UT3 mod RenX multiplayer is kinda dead. After like 2 years of playing, people got bored and started to wait for the actual release.
Ah well, let's hope it'll be here soon.