As far as I understand, the DB containing all the shared data from the other platforms will be kept from GOG, and I don't like very much the idea... I understand that this way, if you install ONLY GOG Galaxy in a new PC you will be able to "see" your progress/games in all the other platforms that you still not have installed in this new PC, but I would have preferred this data to be read only locally at the start, and only if the access credentials are saved directly in the other accessed clients.
Because even reading the FAQ, I still don't know if you have to give to Galaxy your account credentials to the other stores, or if it just runs the respective clients, ignoring id/passwords, to get the data.
This is great, because people will be able to play it before Wasteland 3 comes out in 2020. Funny how things worked out like that.
Edit: I'm working on a new mathematical theory. It states that, given an infinite timeline, all PC games will eventually become giveaways. Right now I'm trying to work out a formula to determine more precisely when each individual game will become a giveaway. I'm thinking impending sequels play a role...