While I cannot ascertain this information from experience as Skyrim belches up a bunch of DLL version errors at me (despite not having those mods enabled), a list of which seems to grow longer with every attempt to run the game, so I can only go by my knowledge of the Steam version, which disables achievements if it detects *any* mods to your game (including the USSEP, which Bethesda feels makes the game too easy). I would surmise you'd need to find a mod to enable achievements, HOWEVER, I only know of such a mod for the Steam version and its achievements. The GOG version probably has a whole different setup.