First, my apologies for the double post; I didn't see my first and thought for some reason it didn't get posted.
(Didn't expect such a fast response either.)
I don't see anything about JPA that would make it inadequate to do what I want, I just see it as an ORM tool used to awkwardly map an object language to an object database. And I agree with most of the comparisons that we've probably all seen on the Web concluding that JDO is a superior API for object databases.
I am not however, married to JDO, although I think it's good. Its lack of true (before commit) pessimistic locking is something I miss, for example, and it to some degree it is a compromise needed to reach an agreement among stakeholders. I'm actually thinking that the people who did such a good job at designing ObjectDB would be able to build an equally superior native API.
Notwithstanding the issues, ObjectDB (especially) and JDO seem capable of doing an excellent job for the business applications I plan on using it for while you're still supporting it.
Is there some link you can provide me with (other than on your site, which I've gone over fairly thoroughly) for more documentation?