Do you actually have to connect online even just for first time to even play this game completely offline? Because that would not exactly make it DRM free if that's the case.
You don't have to connect, I played without neocore account up to level 30-something. Then I discovered that you can't transfer your offline char to online - so I went back to playing offline. Too much time invested, and from what I noticed, online only offers daily global quests in the spirit of "slay 1 million werewolves".
Well, I thought I had somewhat covered that in my previous post (and the fact that usually you can't use offline saves online... you could cheat and all) but sorry it that wasn't clear.
So to sum up, you can play 100% offline (no account, registration or internet connection), but in that case your saves can't be used if you want to play with "registered" characters (neocore accounts, not sure if steam users can also choose between both options though)
I wasn't sure about "private" multiplayer, in other words, Gog galaxy (I would call it offline multiplayer but that would sound wrong and confusing o.O)
The answer is yes. I just tried with a friend. You can play solo & offline, and then use that character to play on galaxy. The con / bad point: since the saves are on the user computer, it's easier to cheat.
Still it is good for the Gog community as it opens up possibilities (it would be way too constrictive if you had to make separate characters, it would reduce the number of people available)
You still cannot join a party that is further in the story than were you are (the opposite is possible though, tried too), and you need to have same version of the game (patch and mod, so people playing with this mod: http://steamcommunity.com/app/400170/discussions/0/490125737479241823
can only play with people who have it)
At least it's possible (even if in a limited way) to alternate between solo and galaxy, so I hope that clarify things for people who might be interested / were wondering
PS: If I'm not wrong, there are only daily quests and events that you can't access offline (=need registration), as you said. It's very cheesy (if not dishonest) of them, since you can't access 100% of the content offline you could say it's not 100% drm-free. Meh, whatever
I think I remember reading sometime ago on their forums that previously adventures were online only, and after the community complained they made it available offline. Doubt it happens with events and daily though