Ah, I have not tried that, so not sure. I swapped computers without any problems, but they both where online.
Hm, from reading their forums I gather it is indeed online activation:
No worries! Our servers won't drop out, and if we (theoretically) ever go out of business, we'll make sure you'll get an activation-free copy.
That's too bad. I mean promises are all well and good, but not really relevant in the business world, so unless that online activation-free copy is not for sale yet, I'll just save my money. I voted for Driftmoon on the wishlist though; if one day it should become DRM-free and available on GOG, I'd happily pay for it. Anyway, thanks for your replies, amok!