@NiLuJe: in simple terms, yes.
What I wrote above was slightly simplified, because Kindlets of course don't only use classes from their own classloader (but from parent loaders too - like JButton), and they are able to spawn new threads (but only inside their own thread group, so these can again be killed as you see above).
I don't know what the "unable to clear static field" is trying to say exactly - it might be related to not being able to re-assign static final members (setting a field to null is a common measure to help the garbage collector, but it won't work on final fields for obvious reasons), or it might be something else.
But yeah, for all practical purposes, just assume that you don't have to worry about cleaning up after yourself. That's one of the beauties of the JVM. I'm starting and restarting Collections Manager dozens, if not hundreds of times during some dev sessions, and I'm never really experiencing issues that could be related to memory management (well, except if I'm doing stupid things myself
).