JDO is Java Data Objects, a datastore-agnostic interface for storing Java objects in transactional datastores.
Participation on the project is via the mailing list and the source code repository. You join by subscribing to the mailing list and participating in discussions. You can help by contributing your ideas, enthusiasm, code, documentation, and tests. The fundamental tenet of the Apache Software Foundation is that great communities build great code. The emphasis is on community; the code comes from that. If you want to help, just join the mailing list, see what needs to be done, and do it. Welcome!
It does - the JDO wiki complements the work taking place on the mailing list and provides additional information on the project.