Paul Ford mentioned Kowari/TKS/Tucana Technologies in his writeup: WWW2004 Semantic Web Roundup.
"Many of the Semantic Web projects discussed during the conference used Jena as a backing store, but one contender to Jena's throne is Kowari, from Tucana Technologies."
"Rather than competing directly with Jena, Kowari includes support for the Jena API, as well as JRDF, an alternative RDF-management API, and adds to these APIs with a new SQL-like query language, iTQL, that can be used via a built-in interactive shell."
The TKS/Kowari presentation can be downloaded here. At the Semantic Web Developers Day Kowari got mentioned during the "Harpers.org: a Semantic Web Case Study", Simile and MINDSWAP presentations.
We should continue to make it clear that Kowari is not really going to take Jena's throne. In the short and medium term I can only see us improve Jena support. The slated FastPath and improvements in ontology speed are both things we're looking at putting into Kowari soon.
JRDF's goal is to be an API more approriate to use for our underlying triple store. With Kowari, we needed a better abstraction of using RDF triples and throwing away everything and doing Jena would've taken too long. The Jena support is basically a mapping of Jena to JRDF (and back again).
It was great to meet a lot of people face to face. And I got a lot of interesting news about various people using or evaluating Kowari. I think it'll lead to some interesting news in the near future.