Like I said, I haven't heard of this project until now, so I don't know the wider context, but it may be that some of the people who are reacting negatively to

Like I said, I haven't heard of this project until now, so I don't know the wider context, but it may be that some of the people who are reacting negatively to it have been burnt in the past by the many other projects that have gone down this route: project starts as open source, then it goes open-core, then over time more of the dev effort naturally moves into the proprietary part, then sometimes eventually they change the license for the open part too. Forking is often impractical in reality as a solo dev or small team rarely has the resources to keep up with security fixes. I'm entirely happy to pay for things, do pay for many things, as well as donate to the authors of projects I use, and whatever this library is seems reasonably priced. Nevertheless, I'm pretty reluctant now to use open source libraries unless they're backed by a foundation, given how many times I've been badly burnt.