I would really like to know where the problem was. If the problem is that GOG's terms are unreasonable compared to Humble or that they simply didn't want to be bothered with providing keys,
Maybe they're worried that if they started handing out an extra set of gog keys, backers would pass those around to non-backers, which would potentially eat into their sales? Especially when they pretty much lived up to their obligation to provide a DRM-free version to backers.
Regardless, here's a quote from Judas
(from the time of the Tesla Effect release, which caused quite a stir, since the developer had, as it seemed at that time, arbitrarily decided that the Steam version will have to be DRM-free enough for backers) regarding how gog handles giving out keys to devs/publishers. If it really is as simple as Judas makes it out in that post, I think that Krillbite might consider giving keys at least to those backers who either specifically ask for them or who are willing to turn in their Steam key in exchange (which might be complicated, as that one is in turn tied to Humble.