The question was not which library could present an AST for all those languages, but which kind of library format can be consumed from all those languages. And ideally without FFI and writing complex wrappers. C libraries non very convenient to use from C#, JVM, JS (node.js) or sometimes it isn't even possible (e.g. for JS in the browser).
The question is important, because otherwise one would constrain editors to be written only in a language which is compatible to the library format.
The question is important, because otherwise one would constrain editors to be written only in a language which is compatible to the library format.