Those are two standalone plugins for VisualVM. Just open them in the IDE, set the latest VisualVM as your platform (you probably need to create your own version of VisualVM from the sources you've checked out, by choosing "Build ZIP Distribution" on the VisualVM application in the IDE and then unzipping the generated ZIP that you'll find in the 'dist' folder). Then everything should be fine, no error marks and so on, as you can see here:
The "Hello World" sample does the same as before, except that it is now updated to the latest APIs:
The second sample, providing the "JVM capabilities" subtab that you see in the bottom right of the screenshot below, shows how a plugin can integrate into an existing tab using the new API and save/restore its data to/from Application Snapshot:
So, if you're interested in integrating your tools into VisualVM, the above are the two samples you should look at. Both will find their way into a tutorial soon.