Not correct, any more.
The generic key have been revoked.
So the game do not work at all without changing the generic key after installation.
The game's copy protection do call home at every game start, and if a key is revoked it is a no go.

I my opinion this game should not have been at GOG at all because of this.
GOG generally stands for DRM free games and this one clearly have DRM.

So wait, if I understand correctly you can't even play single player without connecting to the server?

You can play single player without connecting to the server. Although Zone Alarm firewall has a known issue where it stops you from playing, so you would need to turn it off if you use it.

Best outcome is using a non-zone alarm firewall to stop it calling home.

Thanks, but since that post, this happened: http://www.gog.com/forum/general/defcons_drm_is_still_active_support_doesnt_give_a_crap

I'm now well versed in the intricacies of DEFCON's DRM. :P

No worries; must have missed that thread - I don't normally hit the general discussion pages!