Posted June 14, 2017
Aemony: Right now it only seems to be Fallout: New Vegas, but any new title on GOG that comes with Galaxy integration will most likely be effected. It's also possible that if GOG starts patching old games with the new features that they as well will be affected, though in that case you can simply downgrade or disable auto-updates for those titles and you'll be able to play them on XP still.
So really, only completely new titles are "seriously" affected.
adaliabooks: I doubt it's even that. It's not to do with Galaxy integration, tonnes of games have that and there are no reports of broken compatibility, it's the fact the Galaxy integration replaces Steamworks. So really, only completely new titles are "seriously" affected.
To my knowledge F: NV is the first Steamworks only game we've had here. It relied on that steam.dll to run, and in the Gog version it has been replaced with a galaxy.dll.
For whatever reason the steam.dll still works on XP (and the game still runs sans Steam with it in place) while the Galaxy one doesn't (as Galaxy doesn't support XP anyway).
So I'd imagine the only games effected are those that previously were Steam only and have Steam features. Any old games released before the advent of Steam should be fine, and any newer games may or may not work depending on how reliant on Galaxy functions they are (but any brand new game isn't going to be guaranteed to work on XP anyway).
IMO, it makes it much worse that GOG couldn't be arsed to NOT break the Steam dependency, since it's an exception -- and a rare one, at that.