Due to the interest shown in this topic, I believe it will be beneficial if we have a single place where everyone that wants to have DB2 support in OpenAccess can vote for this implementation and provide comments for specific scenarios.
For that reason I have created an item in the Ideas & Feedback Portal which we can use for that purpose. Feel free to Like it and post any comments there.
All the best,
the Telerik team
Q3'12 SP1 of OpenAccess ORM packs Multi-Table Entities mapping support. Check it out.