I run NWN on a Macbook, and following these instructions worked for me! I also assume that as long as you have the files, the WINE wrapper will work, so you shouldn't worry if you don't have the GoG version.
(Instructions taken from
http://www.gog.com/)
(1) Buy a copy of NWN Diamond from GoG, and download all materials.
(2) Email GoG and ask for multiplayer serial codes, so they will email you new ones (This is the second step because there's a time delay for them to get the codes to you---do it quick for fastest response, mine only took about 24 hours).
(3)
https://www.mediafire.com/?2img3h1oh8j03 - Go here to get doh123's wrapper for the game.
(4) Follow the WINE instructions in the download, and install the GoG NWN setup .exe file from the download (the 2GB file). The instructions with the WINE download are great.
(5) Drop your new multiplayer CD key .ini file (from GoG email) into your WINE "C:\" drive directory for NWN.
(6) Edit your nwn.ini file to disable intro videos, as per the instructions with the WINE. To disable all videos, add a line in your .ini file that reads:
"Disable Videos=1"
(You can search the interwebs for fixes to play the videos instead of disable them. If you find them, post them here!)
(7) Open WINE and run the "premium modules re-installer" .exe file downloaded from GoG, to update your CD keys for multiplayer (instructions for this are in your email from GoG with the new multiplayer CD codes).