Hello I would like to know at what date the gog version of the game will be released

I had also hoping to pick this up on GoG, but it seems they have decided to keep it Steam-only untill the end of Early Access, so I shall have to wait a little bit.
(source: Reddit AMA with DigitalSunGames)
As for how long that will be, in one of the answers in the same Reddit thread they estimated the Early Access to last 8-12 months.

Hi, 8 to 12 months waiting is not "comming soon". GOG should change the game page and give us more informations on the early access or the release of the game...