vv221: The simple fact that I ended up asking this question is a proof that no, the information is not so obvious.
eric5h5: Because you couldn't even be bothered to click on the very obvious link that says "Learn more about early access". I don't think you're arguing in good faith, so never mind, you've clearly made up your mind to be offended no matter what. Have fun with that.
Yes, the buyer needs to understand that they may not receive a finished product.
But the seller also needs to understand that he's going to get some blowback if he ever backs out or starts behaving in an unusual way.
So yes, risks on both sides here.
I think what people get REALLY irate about though, is a total lack of communication. Even leaving an explanatory notice regarding future plans would really help mitigate any blowback the dev would receive. But ZERO communication on the issue is going to be met with hostility, and rightly so in my book.
All he'd have to do is answer, "Why are you removing it from GOG?" I think that's a reasonable question. And you could argue that he doesn't NEED to answer. And you'd be right. But by the same token, people who have given him money don't NEED to shut up about it either, no matter how much it may annoy the dev. These people are also annoyed, and have the right and the means to voice their displeasure. And until that question is answered by the dev, he has to expect that people are going to speculate.