JDO's popularity is growing rapidly because of its simplicity, ease of use, and scalability.
JDO compared to other persistence frameworks like Hibernate ,JPA and EJB3
JDO provides a lot of benefits over those APIs. With JDO you can avoid SQL Lock-In because it eliminates your dependence on a particular relational database product.
JDO’s standardized middle layer insulates the application from the underlying SQL implementation(with JDO implementations like the OR mapper JPOX).
JDO provides a caching lifecycle for persistence-capable instances. This reduces memory requirements and increases the performance of your applications.
JDO delivers significant timesavings to the development schedule by eliminating the need for complex custom-written persistence infrastructure.
Finally: JDO is just about objects!