alt Hacker News> Did you know that there's a compelling legal argument that the GPL attaches to programs talking to each other via JSON data structures?
The GPL attaches to programs that are legally derivative works. So does any other license that doesn't explicitly grant the right to prepare and distribute derivative works, such as the overwhelming majority of commercial/proprietary licenses. The issue is with the overall copyright/legal system, not with the GPL specifically, and given that most entities are comfortable using at least some non-BSD programs it doesn't seem to worry people in practice.
Right, as mentioned in https://news.ycombinator.com/item?id=45096736, simply running GPL programs is probably fine. Input/output that doesn't establish "intimate communication" probably doesn't create a combined work, but "shipping complex data structures back and forth" does, according to the FSF.
There isn't a similar degree of legal risk with MPL 2.0, nor with non-copyleft licenses (which is the subject of this subthread, not proprietary licenses) -- whether or not a plugin counts as a combined work, there are no requirements on you.