You can have others play mutliplayer only if the person hosting is running the full copy of NWN.
Normally when hosting a game, you could run a dedicated server on a seperate PC and then you'd and your friends would all connect to that, so that you were a client machine the same as them. The dedicated server was free, multiplatform, and had lower system requirements.
Because of the copy protection, the machine hosting the game has to be running the full version of NWN. Typically, this would mean that if you wanted to play, your PC would be both client and server. To run a dedicated server with the new module, you'd need a seperate computer, a second licensed copy of NWN, and a second licensed copy of the module.
Bioware has been very supportive of the multiplayer community and they deserve a lot of credit for it, but this is really, really obnoxious. This module more than any other really cries out to be running on a dedicated 24/7 server.