Delixe: The biggest hint it's a multi-publisher deal is the press conference. Activision were a pretty big deal but it didn't warrant a press conference. Neither did Baldur's Gate really, that was just the sweetner to move us out of Beta. It could be that GOG are ready to make thier biggest announcement yet.
I think the press release is mainly for the Witcher 2. Someone from the team posted somewhere the first hour is alone for the witcher, after that starting gog will be involved.
Edit: Ahhh, I can't find this post anymore. So better forget it (especially about the starting times).
Edit2: I'm stupid. Everything is explained in the
official thread: So, first the Witcher, then GOG. Removed the starting times from my post.