BEWARE!: THE GOG GAME IS NOT COMPLETE!
Even, dev is a liar:
Antti: we have to be very mindful on where we pour our resources into. Saving time from implementing a feature like this ensures that the time can be used on improving rest of the game - something which certainly applies to all customers, no matter where they buy the game from.
But, a review tells there are achievements in Steam game only, and they are an important feature:
, d'après les succès Steam, j'ai l'impression d'être passé à côté de bon nombre de secrets.
: "The Steam achievments tell what secrets are still to be find" http://www.rpgfrance.com/test-9975-1-test-legend-grimrock
So, we can say GOG has been owned and is selling a Steam game: a game complete only with a DRM.