Lukas Neukom kindly contributed a proof of concept (source code included) where he shows two ways to solve class loading issues with db4o and OSGi (by either using fragments or by implementing a bundle extender). The idea behind this is very similar to the OSGiDemo but instead of having to register the classes yourself they can be declared in the manifest. Enjoy! (thx Lukas!!).
http://projects.db4o.com/OSGiClassLoading