

GPL does not restrict you from selling the software, though you can’t stop getting distributed by someone who bought it. Even RMS himself sold Emacs back in the day.
EDIT: I’m not saying it’s justified in moral sense, I think it sucks ass. But it’s not against the licence.
BTW one of the maintainer forked it so if you need upgrade path, it exists. (at least for now)
https://github.com/matrix-construct/tuwunel