I have a working solution for exposing server side global datasources to app clients based on:
1. representing datasource definitions as naming References
2. using an ObjectFactory service using aries jndi to turn these definitions into the osgi services needed to supply the datasource from jndi lookups
3. copying all the global jndi entries into the openejb global tree
4. using the openejb jndi transport to pull the datasource Reference back to the app client where it can be set up using step (2) just like all other datasources.
This is currently in the osgi-friendly code I periodically push. I'll work on getting it committed to svn.