rgnrk: Yes, they were officially rejected.
Due to the amount of backers -me included- that opted for a GOG key above any other options, they were going to try again, submitting the final build of the game (the one rejected was a three month old build, from when GOG asked for it). Maybe with that build and if the game gets a good reception it could get accepted. That's, at least, the developers hope. Which, I might add, are extremely nice and are trying the extra mile to please us GOG backer fans.
rampancy: Did they actually promise GOG keys without first confirming that they were locked in for a GOG release? If so, that wasn't very smart of them. Here's to hoping that at least you'll get either the option to redeem the game on Humble, or get a DRM-free download direct from the developers.
They didn't.
In their kickstarter post about the release date, people asked in the comments for GOG keys. So they did an update explaining that they were rejected.
A little bit later they send a survey and many people still asked for GOG in their preferred store, although steam and humble were already confirmed. So they said they would give keys on release day to those that answered steam or humble. As for those that still chose GOG as the preferred store, they emailed us directy and gave as a choice to wait as they would try again, and maybe meanwhile give us a direct link to the drm-free version. I said that would be fine to me, and if GOG didn't work, a humble key would be fine too. So they gave me a humble key.
I'm still waiting for a while, though. In the unlikely event of it being released here, to be able to exchange it, as I wasn't planning to play it right now.