JVider looks cool I downloaded the Demo, and it even allowed me to copy the code it generated.
If however you just need a Java GUI editor that works and that is free. Look at netbeans it allows you to build GUI apps, just like JVider.
Netbeans is not as fast or as easy to use as JVider's GUI tool, it however does a good job.
JVider however does look like an interesting tool.