Ultrastudio.org project uses Java.net for bug tracking, SVN and forum. We were previously using Kenai and still have everything there as well but after posting a lot of spam we cannot even remove (no community manager support) we were forced to migrate from it.
We also use Java.net SVN repository to store the code for applets whose authors have explicitly approved the applet inclusion into Ultrastudio.org project. This repository does not include code that was found on the web under appropriate license (most often GPL) but our attempts to contact the author so far have not been successful. This way Java.net SVN is a kind of "more trusted content" that makes only part of all we have on the site. All checkout links can be found at http://java.net/projects/ultrastudio/sources.
However we are also sure that GPL gives enough permissions on its own to reuse the content. In many cases the author is not reachable because his E-mail is not longer working and the messages we send simply bounce back.
For every applet, it is possible to get the .zip archive of the source code after going to review, then (on the left side bar) going to the applet home project, and there following the .zip link at the top of the page.
Java.net also contains our Discussion on most common problems, found in Java applets.