I was wondering, whether it is possible to run U2F with a fat java client, as I had no luck finding any java libraries that allowed sending queries to the authenticator token. Is such support possible or planed?
If you achieve U2F javascript API into pure Java that can communicate with USB via HID, yes, it is possible. However, as I know so far there's no such JAVA libs so I'm afraid you need to implement it by yourself. But you can do it with C or Python. Maybe JNI as well.