When did you last run steam in offline mode? You do not have to specify in advance, it goes offline if your internet doesn't work. In the past there were problems with it, but not any more. At worst it is the same as disc in the drive protection, but a disc can break and some (like me) don't even have a disc drive anymore, it's an outdated mode of storing data...
Sorry I don't have the dates of my last attempt logged. According to Steam's own page though:
You have to log into steam and select "Go Offline" then click "Restart in Offline Mode". When last I did it, and perhaps it has changed since, you could not log into steam and select "Go Offline" if you were already offline. So you had to know in advance that you were going offline, log into steam, issue the Go Offline command, then you could disconnect and go. I believe there was also a limit to the amount of time you could be offline before steam needed to revalidate though I don't seem to see where this duration is documented so maybe they've gotten rid of it. In any event I'm not saying Steam is horrible DRM but if the game requires steam to be running (in offline mode or not) in order to function then it IS being used as a form of DRM and not JUST a digital distribution platform.
Anyhow - look at Dungeons of Dredmor - it has full steam support including achievements, cloudsaves and mods, but you can run the exe file with steam being closed or even uninstalled and the game will start and work. So the problems doesn't lie in Steam itself but how it is handled by the developer.
How does this differ from what I said? I already stated it is possible to use it as only a digital distribution platform and sure some games do that, listing one doesn't mean anything. My entire point was that Steam didn't have to be DRM but more often then not is. If GalCiv3 is going to be steam only I'd like assurances that it is in fact not using Steam as DRM but I strongly suspect that it is because the vast majority of Steam games use it that way.
I believe it was Stardock's own "Gamer's Bill of Rights" that stated:
"Gamers shall have the right to demand that download managers and updaters not force themselves to run or be forced to load in order to play a game."
In this case Steam is the download manager/updater... if it must run for GalCiv3 to play then it violates their own bill of rights.