Apache Derby is a pure Java, standards-based relational database engine. Derby provides an easy to use data management solution for software developers with zero administration for end users. Derby runs on any J2SE 1.3 or higher virtual machine and supports J2ME/CDC/Foundation. Derby's database format is platform independent allowing databases to be copied to any machine type.

Apache Derby is an open source subproject of the Apache DB project, licensed under the Apache License, Version 2.0.
http://www.apache.org/licenses/LICENSE-2.0

You can find Derby on the web at:
http://db.apache.org/derby/

Apache Derby releases can be downloaded from the following page:
http://db.apache.org/derby/derby_downloads.html