I've recently been putting builds of Kowari 1.0.5 onto SF's CVS server. This has lead to some good feedback; after some initial bug fixing. It's focused what to work on and the practical up shot is that you can now do RDQL queries (found in org.kowari.store.jena):
RdqlQuery q = new RdqlQuery("select ?x ?y ?z WHERE (?x ?y ?z)");
QueryExecution qe = new KowariQueryEngine(q);
QueryResults results = qe.exec();
This converts the Jena-based query object to Kowari objects, which are then processed by Kowari's query layer and returned as Jena objects.
The only query that it currently doesn't handle, although it soon will, is repeated variables in the constraint like:
where (?x ?x ?x)
There's also recent work on client/server JRDF and Jena, N3 input and output, file upload/download from an iTQL client to/from the server, NOT (unstated) constraint, and other improvements.