So this seems to have happened because Youtube wants The Blender Foundation to agree to have their videos monetized. I'm not clear if they want that because of bogus copyright claims, EU legislation etc, or just because they favour making money over not making money? Edit: Either way looking for alternatives seems like a good idea.
I am pretty dismayed to be this right. I didn't think YT would be nearly this aggressive in service of the ideas I outlined.
Basically, they take a cut off that activity. In some cases they could take most of or all the money, which is a clear win for them, but even when they pay out they're earning revenue on the transaction. It's been their core business model, so the problems with advocating an adfree behavior become obvious.
I would add that this becomes more urgent if they're in crisis. Makes me wish I could get the master copies I'd uploaded back, but there's no chance of that.
Bottom line: shots fired. You must work with YouTube the way they want you to work with YouTube, or you'll get punished.