I've posted this in the thread linked above but I think this deserves to be posted here as well:

It is correct, we asked GOG to remove the demo and we are sorry for the confusion it has caused. :( When we released it, it was meant to be a time-limited demo of a prototype version of the game, not much different from open betas or preview demos of other games. That demo period got extended when we postponed the release date, but it was never intended to last forever.

We’re a small team and we couldn’t keep the demo up to date with internal builds without significantly slowing down the game’s development. If the demo stayed online, it would drastically misrepresent what the game has to offer - the full game looks and plays differently.

We treat all platforms equally and that’s why when the demo was gone, we wanted it gone both from Steam and GOG. That said, we should have been more clear about that – we appreciate GOG’s DRM-free policy, and we understand it might have taken you by surprise. We’re sorry. Rest assured that nothing like this will happen to the Early Access version or the full game.