IBM's Lotus Expeditor (http://www-01.ibm.com/software/lotus/products/expeditor/) includes the DesktopEE JRE which is described as:
"The default Java™ Runtime Environment (JRE) of Lotus Expeditor is IBM's J9 VM with the DesktopEE class libraries, an IBM-optimized subset of Java 5 that offers a smaller footprint and faster class loading than standard Java Runtime Environments."
My understanding is that it is a superset of JDK 1.4, so should run fine with Derby. The test harness needs to be updated to recognize this JVM so we can test with it.
http://publib.boulder.ibm.com/infocenter/ledoc/v6r2/topic/com.ibm.rcp.tools.doc.appdev/devapps_developingwiththejcldesktopjre.html for more information on DesktopEE.