To use GSC MoHAA successfully, you need each of the following:
GSC MoHAA can be used on basically any Macintosh, but do note that running a game server is basically as heavy as playing the game itself. In it's memory, the Mac has to build a virtual 3D world in which all of the players run around. Each player also causes about 3 to 5 kb/s of data traffic on your network. If your processor or network is not fast enough, you may have to limit the number of players that can log on to your server.