Yeah but now try to make your Java library useful to a C#, Go or Python application.

In the case of Python I think you could produce something like Jython that runs inside the Java runtime and lines up

https://openjdk.org/jeps/454

with the Python FFA so you could run things like numpy inside of it. Would be transformative for my side projects.

Nothing, hence my "unless they run on the same VM" comment.