Famously so. The main method of deployment was an offline installer before they made Galaxy, and AFAIK Galaxy just downloads and runs the installer.
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.