KAON source and binaries have been made available for download. KAON supports "...ontology evolution, ontology modularization, concurrent ontology access and transactional processing. Storage mechanisms currently include RDF models or a relational database." The Ontology Registry is "...a tool that provides mechanisms for registering and searching ontologies in a distributed context. Ontologies can be searched based on their content, by matching ontology elements against WordNet". Other modules include: the KAON portal, an Ontology modeller and a text to ontology tool (a text mining tool).
The Ontology Modeller is interesting in that it supports search (using the Ontology Registry) including searching on instance, concept or property. From the manual.