If you're going to break the social contract, just do so. Jumping through hoops to complicate the matter doesn't solve anything.
Compare to a take-a-penny-leave-a-penny tray from an era past. You are legally allowed to scoop up all the pennies into a bag, and leave the store, then repeat at the neighboring store, and make a few bucks. You'd be an asshole, but not face legal trouble. You "followed the rules" to the letter. But guess what? If you publish an easy how-to guide with "one weird trick" for making some quick cash, and people start adopting your antisocial behavior and emptying out change trays, you've forced the issue and now either a) businesses will stop offering this convenience or b) the rules around it will be tightened and the utility will be degraded. In the concrete case of Anubis, the maintainers may decide to stop contributing their time to this useful software or place a non-FOSS license on it in an attempt to stop gain-maximizing sociopaths from exploiting their efforts.
I even it out by how I prioritize feature requests, bug reports, and the like :)
I didn't implement this out of fear or some lack of courage. In fact I had the original avatars up for quite a while. I simply wanted my own logo so visitors wouldn't be potentially confused. It seemed to fit the use case and there was no way to achieve what I wanted without reaching out. I didn't feel comfortable bugging you or anybody on account of my tiny little no-traffic git forge even though, yes, that is what you politely asked for (and did not demand).
I think if you do feel this strongly you might consider changing the software's license or the phrasing of the request in the documentation. Or perhaps making it very clear that no matter how small, you want to be reached out to for the whitelabel version.
I think the success story of Anubis has been awesome to read about and follow and seeing how things unfold further will be fun to watch and possibly even contribute to. I'm personally rooting for you and your project!
Your analogy to me seems imprecise, as analogies tend to be when it comes to digital goods. I'm not taking pennies in any sense here, preventing the next person from making use of some public good.
You can make a similar argument for piracy or open source, and yet... Here we all still are and open source has won for the most part.
The GPL protects users from any restrictions the author wants to use. No additional restrictions are allowed, whether technical or legal.
In this case, the restriction is social, but is a restriction nonetheless (some enforce it by harassment, some by making you feel bad).
But you could ignore it, even fork it and create a white label version, and be proud of it (thereby bypassing the restriction). Donate voluntarily if you want to contribute, without being restricted technically, legally, or socially.
Some project even took it to the next level and displayed a furry porn. I think anime and furry graphics are related, esp. in the weird obsession of the people to shove it to the unsuspecting people, but since it's "cute" it's passable. Well unless it gets into the porn territory.
On the other hand I applaud the author for an interesting variation of making the free product slightly degraded so people are incentived to donate money. The power of defaults and their misuse.
Personally I'm not fan of enshittification of any kind even a slight one even when it's to my own detriment.
Except the author is not shoving any stuff at you. Author doesn't owe anything to you and can do whatever they want and you doesn't owe the author the obligation to use their software.
It's not business, it's a person giving something free to the world and asking people who uses it to play the game. You can chose to not play the game or to not use it, but you can't act like your issue with an anime character is the author's fault. Just don't install it on your server and go ahead.
Are you sure you have the right pronouns for Xe?
This is your weird association and hang-up. That's on you to deal with, not Anubis or the rest of the internet.