WordPress is an open source project, and part of being an open source project is you don't really have a right to demand that people not mooch off of your work, at least as far as most open source licenses are concerned [1]. If you don't like that, well, then open source isn't for you.
The other major complication here is that Matt has thoroughly mixed his several roles together, so you have to spend time untangling what is Matt-personally, what is Matt-as-his-company, and what is WordPress-via-Matt. When you untangle that, the core demand appears to be that Matt (in who knows what role) demanded that WP Engine compensate Matt-the-company for its use of WordPress-via-Matt resources being provided by Matt-personally (that no one knew was being provided by Matt-personally as opposed to WordPress-via-Matt). Given the thoroughly tangled mess of that stuff, and the fact that--in the past--Matt made several steps to untangle the ownership of everything, I am not particularly persuaded by the logic of "I'm just trying to get them to pay their fair share," as they're not being asked to pay the people they should be paying.
> why is Matt / WP Foundation acting unfairly by asking for payment?
Because they're asking someone to pay, not the foundation whose resources they are allegedly using, but their largest competitor (a very distinct legal entity).
[1] There are licenses that do have clauses that let you take action, but generally having such a clause makes it not Open Source-compliant, and frequently the relicensing needed to bring the current licenses to that state involves a lot of drama.
WordPress' GPL license guarantees you access to the code and specific rights. It doesn't guarantee you access to the the WordPress database repository of plugins and themes.
WordPress could, in theory, make the repository free for access to all except larger hosting entities that put more of a strain on things, for which there is a fee or throttling. Possibly even indicating this within the WordPress admin UI which flavor of access the user is getting. "Pro" vs "Free" for example.
Note that I am not a lawyer, this is not legal advice, and this is based on my understanding of open source licenses like the GPL over my 20 years working on PortableApps.com.
w.org infra was said to be owned by the foundation for the community.
Automattic's lawyer told the community the same thing.
Volunteers built in to WordPress core dependence on W.Org infra on that understanding. there are over 1500 hardcoded references to W.org infra.
Now those volunteers find out it's "Matt's personal website" and he can do what he likes with it. Including banning volunteers who's livelihoods depend on it for nothing more than reacting to a post with a disproving emojji.
The other major complication here is that Matt has thoroughly mixed his several roles together, so you have to spend time untangling what is Matt-personally, what is Matt-as-his-company, and what is WordPress-via-Matt. When you untangle that, the core demand appears to be that Matt (in who knows what role) demanded that WP Engine compensate Matt-the-company for its use of WordPress-via-Matt resources being provided by Matt-personally (that no one knew was being provided by Matt-personally as opposed to WordPress-via-Matt). Given the thoroughly tangled mess of that stuff, and the fact that--in the past--Matt made several steps to untangle the ownership of everything, I am not particularly persuaded by the logic of "I'm just trying to get them to pay their fair share," as they're not being asked to pay the people they should be paying.
> why is Matt / WP Foundation acting unfairly by asking for payment?
Because they're asking someone to pay, not the foundation whose resources they are allegedly using, but their largest competitor (a very distinct legal entity).
[1] There are licenses that do have clauses that let you take action, but generally having such a clause makes it not Open Source-compliant, and frequently the relicensing needed to bring the current licenses to that state involves a lot of drama.