We don't need credential level information, but something like "you upload to a specific folder, run a script, and it gives you X output on success and Y output on failure" would certainly demystify some of this.
Did you look for answers in the public part of our GOG Developer Docs
? With any specific follow-up questions, it would be best to send a Support ticket so they can be forwarded to people most fluent in this topic.
Wait a minute, you expect devs to build their sources against galaxy instead of standalone exe files? This is certainly what these docs seem to be suggesting. No wonder some devs are having trouble keeping up to date: they have to build using galaxies tools to update. I'm sure there's some sort of workaround, but if I was using certain dev tools that were not as easily tied to galaxy, i could see why that could cause some trouble. It would certainly explain why games like Recettear disappeared.
EDIT: Oh, nvm, i spoke too soon. The term "build creator" isn't intuitive. Most devs would see that as a GUI version of your command line tool. Usually devs use the term "build" to reference the process of compilation.
This seems to be precisely where the rubber hits the road: https://docs.gog.com/bc-build-game
EDIT again: According to this, we could theoretically demand branch numbers from devs if they want to blame gog, since they need to publish to a branch before gog will create and installer. Offline installers would be off the Master branch, but by giving us the branch number, we could presumably somehow use galaxy to verify the good faith of a 3rd party blaming gog for tardiness on updates. Since the developers would want to show their good faith, it shouldn't be a problem for the devs to give us a name to a "public branch."
This does indeed restore a degree of cofidence. Next time i run across a dev blaming gog I'll have to get their take on this.