Screaming Penguin - Source Does Matter

Apache Derby, the database formerly known as Cloudscape and which has moved through changing corporate hands 3 times in the last 5 years, has graduated from the Apache Incubator and is now 10.0.

I recall Cloudscape as being the DB that BEA shipped with all their developer copies and used in training classes. It is a much more full featured DB than Hypersonic/HSQL, and I honestly expect to see it overrun HSQL in the next little while.