Saw on 3D Gamers that there is a dedicated server update for the UT2003 Mac demo available on the Unreal Technology website. According to the Unreal Technology site, "This fixed version lets demo dedicated servers host for retail UT2003 clients on any operating system. Without this fixed version, you can only host other 2206 demo clients.". It also mentions that "The retail game (shipping June 11th!) has this fix. This is for the initial public tech demo only!".

The 3Mb update is available from The Official Website and 3D Gamers.