If I remember correctly, the CD copy of Nox came with a disc to allow multiplayer with just one purchase. I'm working on downloading and installing it on my wife's computer and was going to see if we needed another license, but I wanted to ask here in the meantime.

Thanks for your help!

Edit: Works!

If good, you can install nox anywhere with the gog version, which means you don't need a second CD to run multiplayer only.