JGraph (the last version of which was version 5) and JGraphX (which was originally going to be called JGraph 6) are completely different code-bases. JGraphX was a complete rewrite from scratch, which is why we made the naming change to avoid the idea you could upgrade from 5 to 6.
So no, there is no migration route, you'd need to re-write your part of the application that interfaces with JGraph(X).