It's worse than just self-signed applets - recent Java versions change some of the security settings, and won't run those applets because of issues with the manifests. You need to lower your Java security settings to Medium.
I suppose you could try and sign those packages yourself, but it's probably not worth the effort right now - HP is moving towards HTML5, away from Java. If you go to Resource -> Custom View, pick a Custom View, then select the "Topology" radio button, it will display the topology using HTML5.
But if you go Resource -> Network Topology, it will use Java. I'm hopeful that HP will soon remove these last remnants of Java, and move it to all HTML5. That is certainly their clear direction, I'm just not sure what the timing will be.