Database Partitioning Feature is available for DB2 9.5 and DB2 9.7 (all fixpacks), but its name has changed to InfoSphere Data Warehouse in 9.7. But you can just apply the InfoSphere Data Warehouse license file on to an existing ESE installation and you are all set with DPF.
DPF (hash partitioning across multiple nodes) is different than Table Partitioning (also known as range partitioning on a single node, often times by a date column, etc) which is included with DB2 ESE 9.5 and 9.7.