The running game can also call out to Galaxy and unlock, or not unlock, ingame content based on what it hears back. It's pretty difficult to imagine a definition of "digital rights management" that doesn't include this.
In version 1.0 of the GOG release, multiplayer is enabled.
In subsequent versions, multiplayer is disabled (in the sense that the button to host or join a game is greyed out) unless the game succeeds at verifying you through Galaxy. (And this is a dynamic status; you can have it enabled, shut off Galaxy, restart the game, and find that it's disabled again.
But apparently that isn't DRM.