I don’t think it’s understandable in this case, no.
The entire project depends on Wine, imagine if Wine devs restricted Bottles in what way they are allowed to use it just because Wine project doesn’t want to deal with bugs potentially introduced by the Bottles dev.
But they won’t, because of the license.
And neither can the Bottles devs.
If they want to have total control over their source code, fine, but then they cannot claim to be open-source and release it under GPL.
Yes, and another big difference is that Bottles refuses to provide any kind of help to package maintainers.
According to maintainers’ comments on the Github project, they have to figure out how to build it by trial and error.
I was actually really surprised that there’s isn’t any kind of build documentation.
It’s pretty unusual.