I decided to respond to this question by OP, near the start of page 4, as it is relevant to what my response is, and I cannot be bothered reading any more replies.

When you don't know something, then you go with what you do know.
And what I do know, is that there is a contradiction going on between what GOG is and what it stands for and has enabled for all of us, and the accusations being mentioned in this topic. In short they don't make sense.

I imagine, that there is a very good reason why GOG does things the way it does, though like everyone, they aren't immune from mistakes from time to time.

Why would a store like GOG, which has gone against the mainstream, for customer benefit, that seemingly has our best interests at heart, be treating game providers in an uncaring manner?

I don't think they are. Instead, I think they have very good reasons for why they might reject a game, and they aren't always obvious.

I imagine that amongst all the possibles or probables, that it has to include at least some of the following.

1. Time constraints. How busy exactly are GOG?
2. Surely they work to some kind of schedule, but leave an opening for special or surprise occurrences.
3. When they add a game, it would not just be a matter of adding a name to the game list. They have to setup a Web page, do some research, test out installers and who knows what else. Not to mention, give support.
4. They need to make enough profit to cover any effort or time they put in.
5. There would undoubtedly be priorities, when it comes to what they want to spend their time on.
6. There is real competition out there, and they need to survive, especially as GOG is still very unique in many ways.
7. How do they wish to be perceived, especially in light of survival? For instance, should they be seen as a mostly Old Games and Indie Games store? Or should they be making sure that they attract as many mainstream buyers as possible?
8. If those who provide games at GOG, don't get enough sales, because not enough customers are mainstream, then they are going to be less encouraged to sell games at GOG, than many of them are already, and GOG only survives because of the support given by game makers or providers. It doesn't matter how much money we have to spend, if GOG doesn't have suitable product.
9. There must be factors relating to price and inclusions etc that decide whether a deal is even possible.
10. Bound to be other things we are just not privy to that are quite sensible and logical.

So anyway, that is my 10 cents worth.