ERISS: GOG has nothing to do with Steam (was troll?).
No, not troll. The answer is valid for either versions of the game. I forgot who said it, but GOG and all other distributors have the same version, except for those who distribute the Steam version have Steamworks integration in the builds.
The point is if you apply one of the lines listed to your command line arguments (which the Steam equivalent is "launch options"), it'll work for the GOG version. In fact, that is what the GOG language changer does, albeit in a bloated multi-megabyte binary.
It's the same game regardless where you buy it. I don't discriminate against the Steam forums just because I bought the game at GOG. I also share posts from the GOG discussions on Steam where useful, and sometimes post announcements from the developers if they don't post here within a certain period.
(BTW, not wholly related to the discussion at hand, I prefer to figure how things work on my own rather than delegate them to some tech support. Not that I have anything against GOG tech support (in fact, never used them), but that's just how I go about solving problems. As I said, not related.)