Oct 22nd 2010 - As per their marketing announcement. "Salesforce.com and VMware introduce VMforce : the first enterprise cloud for Java developers. With VMforce, Java developers can build apps that are instantly social and available on mobile devices in real time. And it's all in the cloud, so there's no hardware to manage and no software stack to install, patch, tune, or upgrade. Building Java apps on VMforce is easy!" So this is a cloud-based service and has a datastore that is not RDBMS. It provides JPA persistence using a plugin for DataNucleus.
A further example of why the DataNucleus architecture for flexible standards-based Java persistence to any type of datastore makes perfect sense.