I don't want to sound ungrateful -- I'm very happy that Civilization made it to GOG.
I have to ask though -- what about the Mac versions? At least for Civ IV a native version exists and is in the app store.

There are also some problems with newer MacOS versions, I believe since Yosemite. The troublemaker here is Python, as Apple changed the used version of it and the backwards compatibility isn't working here as it should. You can still fix it for the expansions, but don't ask me how exactly to do it. As far as I know the vanilla version is not fixable. So if GOG really gets Aspyr onboard and some nice mac ports, I'm pretty sure the mac version of Civilization 4 will not be added to the catalog.