This just makes me worried to rely on uBO but more because what if the author just fucks off because someone else pissed them off.

That is very concerning to me, also.

Large parts of the internet relying on one or two tiny one-man FOSS projects? (UBO and ADguard are often cited as the only two reliable-ish and safe adblockers)

If he can’t be bothered with that nonsense, how secure is UBO’s future? How secure is the future of adblocking?

I would bet that advertising companies are rubbing their hands now and planning to ramp up pressure against these poor devs.