Gemini JPA is distribution of JPA provider infrastructure that allows it to be used in a modular environment. It currently supports OSGi and is an implementation of the OSGi JPA specification. If you are wanting to run JPA in OSGi then Gemini JPA is the product for you!
This guide is targeted at those who are at least partly versed in OSGi concepts and API’s. It offers examples of using Gemini JPA but is not going to be the best reference for learning OSGi from scratch. If you are looking for OSGi information please refer to one of the references in the back of this guide.