You can certainly have links connecting to links in JGo as well as in GoDiagram, since the designs are very similar – just have the JGoLabeledLink’s MidLabel be a JGoPort.
I believe you could translate the GoDiagram sample code into Java & JGo. I don't know if there are any gotchas that would make it difficult to complete. One issue is that there isn't a JGoViewEvent for having the selection dropped onto an object (or onto the background of the view).