> That's a pretty shitty thing to do, in my opinion.
The founder and main developer has shared some of his thoughts in this matter here: https://marijnhaverbeke.nl/blog/sustainable-maintenance.html
He has put thousands of hours into these projects, and are giving them away for free – that is, if you can stomach the slight hint that if you're making money on it, then maybe contribute a tiny bit.
He hasn't blogged about burnout yet, like many other open source maintainers do. A recurring theme is about toxic community members. I hope he scrolls past your comment.