Fedora 2.0 Release Notes "Fedora 2.0 includes significant new features and improvements including the introduction of the Fedora Object XML (FOXML) schema as the new internal storage format for objects, introduction of the Resource Index that provides enhanced search capability, introduction of a Batch Modify utility, upgrades of all third party libraries, performance enhancements, and a number of bug fixes."
Kowari is mentioned in "Fedora: An Architecture for Complex Objects and their Relationships": "Fedora expresses relationships by defining a base relationship ontology using RDFS  and provides a slot in the digital object abstraction for RDF expression of relationships based on this ontology. Assertions from other ontologies may also be included along with the base Fedora relationships. All relationships are reflected in a native RDF triple-store using Kowari . The query interface to this triple-store is exposed as a web service, providing a rich information foundation for external services."
Looks like there's some Trippi work too.
Chris Wilper and Edwin Shin both have contributed back to Kowari too. Most recently, with changes to the DateTime datetypes in the post-Kowari Pre-Release 2.