JPOX is a free and fully compliant implementation of the JDO 1.0 and 2.0 specifications, providing transparent persistence of Java objects. It supports persistence to all of the major RDBMS on the market today, supporting all of the main Object-Relational Mapping (ORM) patterns demanded by today's applications, allows querying using either JDOQL or SQL, and comes with its own byte-code enhancer.
JPOX is available under an Open Source Apache 2 license, allowing access to not just a top quality Java persistence implementation but also to the source code, allowing you to contribute to the success story of the principal Open Source JDO implementation in the world today.
JPOX 1.0 implements the JDO 1 specification and passes the JDO 1 TCK. JPOX 1.1 (currently under development) extends the JPOX 1.0 capabilities to implement the JDO 2 specification. JPOX 1.1 will become the JDO 2 Reference Implementation with its 1.1-final release. JPOX will be updated in future to also implement any EJB3 specification of Java persistence.