There are ways to require payment for some uses of things that are legitimately open. As an example, consider the practice of selling exceptions to the GPL, as is done for Qt.
There are people who do not consider that "open".
See the whole debacle about what exactly constitutes "open source"
Who? Even Richard Stallman is okay with what they do: https://www.fsf.org/blogs/rms/selling-exceptions
In any case the software world has changed drastically since that article has been published.
"open" is not like 1+1=2. ultimately it is arbitrary. one definition of open is "to make available", by that definition all of them, including CockroachDB are "open".
open does not necessarily mean you can use it, just like how an open door does not necessarily mean you can enter the house.
in any case, we can agree to disagree.
"Open source" is defined by the Open Source definition according to the OSI [1]. In saying that, I realize that every couple of years somebody tries to claim that their understanding of the term "open source" should trump the one the community has settled on. I personally am not ready to acquiesce to this semantic drift, at least, not yet.