I am looking for a serious graph database system which is not written in Java.
I am not interested in RDF databases, since I expect to be able to store more complex graphs (actually hypergraphs) From within the Java camp, OrientDB is a good example of what I am looking for.
Disclaimer: This is not flamebait. I have nothing against Java, I just want to have an idea of what is out there, implemented in other languages, perhaps as an extension to other dbms, such as MySQL, MongoDb or CouchDb.