can’t say much about Java, it doesn’t look like it’s being worked on for quite some time.
The same is true for Clockwerk, though that is at least somewhat usable. I’m playing around with it and some clips from BeGeistert at the moment. All the source is at OsDrawer and waits for a good soul to develop it further. Originally, it wasn’t planned as a video editing app, but to create all-day looping multi-media advertising/presentations for malls etc. The usage is a bit awkward at times…