Does Opensolr support the JTS Polygonal Geospatial search?

Yes, Opensolr now supports the  JTS Topology Suite, by default, which does not come bundled with the default Solr distribution.
It should be enabled in most of our servers and datacenters, however, if you feel that doesn't work for your index, please Contact Support and we'll be happy to enable it for you.
No further setup will be required on your part.