TypeDB is an open source, freely available, strongly typed graph database. Vaticle, the company behind it, offers commercial licensing and enterprise support.
Vaticle positions TypeDB as an operational database which, like knowledge graphs, supports ontologies and inference without requiring the use of standards such as RDF and OWL. The idea is that it uses strong typing to create a natural, high-level, and easily understood data model that prioritises the relationships in your data while also embodying object-oriented programming principles, such as inheritance and polymorphism. This is then combined with its pattern matching and inference capabilities.