I have been granted write access to the CVS repositories of GNU Classpath and Mauve. I have also started messing with GCJX (again) that was started by Tom Tromey. It has come a long way since the last time I had taken a look, but it sure can use some help from willing hackers. Would you like to help develop a first-class Java compiler?
By the way, Tom has become one of the Java front-end maintainers for GCC.