More on Java DB
Java DB is Sun's distribution of Apache / Derby technology. You can find more about Java DB here.
Currently, a global Sun engineering team of database experts is actively participating in the Derby community and working to incorporate other useful features in Derby: SUR and JDBC 4. Sun also makes nightly test results and builds of Derby available to the Derby community. We have also put in place a rather extensive test infrastructure which includes long-running and robustness tests. So, you can expect continuing contributions from Sun in these areas. You can always turn to the Apache / Derby website to learn more about current activities, and if you're a database expert, consider making your own contributions.
In the meantime, if you're a database user, you'll be rewarded by taking a look at the small and mighty Java DB!
Check out the Aquarium for more useful links on Java DB.
Finally, for the more curious among you who have an interest in history and software "archeology," I should add that this is not the first time Sun distributes a database technology. In fact, the ancestor to Java DB, i.e. Cloudscape DB, was distributed by Sun along with the early reference implementations of the J2EE platform going back to 1999.