clarry: There is some optimism among tech companies and the free & open source software community that reimplementing APIs is OK.
GOG seems to think so too: they have implemented a Steam SDK wrapper which should allow some Steam builds of games to run with no (or minimal) modifications on GOG:
https://docs.gog.com/steam-sdk-wrapper/
That's a good thing, then, and I also think it should be OK because the more widespread the API is, the more it becomes an issue of interoperability, which AFAIK already has been ruled OK. So, by becoming the de-facto standard, Steam may have crossed that line anyway, even without further court decisions.
clarry: (This is still an unfavorable position for GOG because they are forced to play a cat and mouse game where Steam can constantly change the API and make more work for GOG. However, it may be better than trying to get every developer on board to implement Galaxy integration)
That would inconvenience all developers on Steam, so it's probably going to be (ab)used for some big stuff in order to slow down competition, instead of constantly nagging everyone. But then there'll have to be a compatibility layer for de-facto abandoned games that still are selling on Steam, so it might actually be infeasible.
MarS666: I understand that it's annoying to create an update for 6 different platforms 3 times a month. But why is it too much effort to update a game once a year?! If I know I don't have any more updates planned for my game, why is it so hard to create a final patch? These kind of developers should really be boycotted, here and on Steam.
True, especially if the wrapper mentioned above actually covers everything, this is even less understandable. Once a year should indeed be doable, and I would much much prefer to know that eventually (even if it takes said year) I will get the complete version than getting promises and gambling or looking up lists of bad-apple publishers before every purchase. If the posts about the subject I've read around here are any indication, this might apply to most, even to those who are relatively comfourtable buying on Steam instead of here but still have a mild preference for GOG.
And if nothing helps, there are measures that can be taken before delisting a game, like starting to deduce increasing amounts from the purchases going to publishers, up until witholding them entirely. In theory, one could even implement fines for lack of timely updates, but putting that in the agreements might just scare away smaller teams.
It might be interestiong to compare the sales percentages of day 1 listings on GOG with those of 3 months after listings. I'm sure that GOG has done such comparisons since they can at least ask CDPR for their stats. If people are spending premium just to have early access for 3 days or maybe a week, then there has to be a big difference there, and this alone might be what's keeping GOG down and the publishers should know better from their own figures than blaming things on GOG being small and unimportant.