It looks like the Pentaho team made some nice work in the creation of a new OLAP UI called Saiku. Wouldn't it be an idea to implement this new UI in replacement of jPivot.
(Maybe it's better to offer both in parallel in the beginning as their might still be some small glitches in it even though it's version 2.1 RC already)
Would be great to see Saiku instead of JPivot in Jasper.
Saiku is now in version 2.4 - they changed there license zu Apache License V2. There is a thread discussing this: http://ask.analytical-labs.com/questions/1077/saiku-on-jasperserver-ce