I tried to raise an issue on the github repo but it would not accept my submission.
The current code in the Main class fails because the returned registry is null.
UpnpService upnpService = new UpnpServiceImpl();
upnpService.getRegistry().addListener(listener);
upnpService.startup();
Reorganized like this works.
UpnpService upnpService = new UpnpServiceImpl();
upnpService.startup();
upnpService.getRegistry().addListener(listener);