Hey all I'm interested in buying some DnD games so I could (hopefully) find/play with others online. However, I can get the DnD games cheaper elsewhere and I was wondering if I could play co-op/multiplayer with others who got the game elsewhere.

Here's what I mean. I can buy the DnD collections off Gamersgate for cheaper than on GoG (NWN series only because it has both 1 + 2 where as GoG has only 1). Will I be able to play them in co-op/multiplayer with people who bought off GoG or other sites? (I know that I would on official servers but I don't know if GoG has their games linked to different/fan matchmaking servers etc if the official matchmaking servers are down).