Leroux: Hard to say, without knowing the game. Usually they'd put
DRM-free if it was DRM-free, but they also labeled "World of Goo" as
Other and as far as I can tell their version is DRM-free. Maybe they put that because you need to be online to see other players, but the installs and runs perfectly well without internet connection.
thme: The game is Neverwinter Nights and it can be a multiplayer. As long as I do not have to be on the internet while the install runs...
I didn't buy NWN from GamersGate, but that one definitely uses serial keys. I never heard that someone had to connect to the internet to install it though. But in case you didn't notice yet, someone who reviewed it said:
"This particular release is not as described, "fully up to date", after installation you will have to download an extra patch, which should only take a couple of minutes, then you are ready to go!"
(If you're hesitant or suspicious, get it from GOG for $10. But I guess it's currently $5 for you on GG?)