In the multiplayer demo, if a server has been modified to allow for all four gametypes, you can join without having to download anything. If you want to host a game, a small (less than 3k) pak file needs to be installed that will unlock the additional modes. It's made by ReKast and the filename is ReKast-GameModes.zip. One place you can find it is here:
http://63.101.132.103/~gator/MOHAA/
Have fun. Team DM is vastly superior than regular DM, IMHO, even if you're stuck with just one map till the full version is out.
[This message has been edited by Creole Ned (edited February 03, 2002).]