onemodel looks good. I'd love it as a knowledge graph editor that focuses on information from a personal standpoint. Would be interesting to map the data model to RDF.
If it had RDF export would that make you a user? I need feedback (eg, users) now (along with some prettifying and installers). I invite you to join the discussion list and continue this.
Thanks for the comments.
I'd be interested in why RDF is important (ideally, on the OM discussion list :). To me, OM is better than the semantic web (on which I am not an expert), for reasons I try to explain in OM's FAQs.
Java has many good RDF libraries such as Jena.