It has always been part of the EULA that you can't make money off of Minecraft in any way. Always. Every player and every server owner has agreed on that they can't make a single dime. They've known right from the beginning that everything they'd do to gather money for their servers would be technically illegal. But obviously they were okay with that, because they accepted the EULA. And I honestly doubt that Mojang would make _official_ statements that negate their own opinion.

Later the EULA was changed so that video creators could make money of their Minecraft videos. And now, Mojang is changing the EULA again, so that server owners can make money. They just need to keep in mind one thing:

Anything you buy with real money can't give you any advantage in gameplay.

That'd be called pay-to-win and I think everyone agrees that pay-to-win should be avoided at any cost. Would you say that inviting you to play Banjo-Kazooie and then selling you jiggies for .99 € the piece would be okay? I doubt it. And that's point: Buying rewards is not donating.

People who wouldn't "donate" without receiving a fancy but useless item in return don't give two knitting moose about the server. They just want diamond swords or whatever they're being offered FOR REAL MONEY. That's not only unethical, I'd go as far and say that this is a grade A rip off. If your server can only survive by exploiting its naïve users, I'd seriously reconsider whether it is even worth being saved. No offence, but get creative and find a way to raise money without robbing little kids.