That's... weird.
I've evaluated front-end frameworks in the past and considered both free (open source and no cost) against commercial. I can't explain why, but the mandatory donation for commercial use just rubs me the wrong way.
(And don't get me wrong, I've published my own basic HTML templating library here: https://www.npmjs.com/package/pogon.html)
Perhaps I can explain it this way: If I'm doing a hobby/learning project, there's no obstacle to using Mizu. But, if I'm a rank-and-file employee, experimenting, setting up the $1 / month donation is actually a huge obstacle. It's not the cost, it's the actual act of handling money. Furthermore, Mizu will need a lot of paying customers for the monthly donations to actually pay for anything substantial.
Personally, I would think more carefully about how to derive income from Mizu.