I really want to provide a real polyfill for ie9+ but I think it's gonna be hard :p.
I'm still thinking on use case where globality would help it with isomorphism, in my view all isomorphic scripts being loaded/required via some kind load manager anyway, so all the dependencies get explicitly defined.
And nothing goes global.
Or did I miss something?
Well with browserify and webpack you can specify requires within the config as well, (usually a good spot for polyfills), which simply requires the file without having to do it explicitly in app code.
Since in the browser you are expecting form-data to be there it makes sense to make it global anyway since it would help people transitioning from dom code to isomorphic code.