Awesome. Been looking hard for open source datalog-supporting data stores and data processing systems for a couple of years now. This is at least something in this direction, although I might ultimately wish for a full-fledged database or system that could run in a distributed fashion if needed.
RDFox: "A highly scalable in-memory RDF triple store that supports shared memory parallel datalog reasoning. It is a cross-platform software written in C++ that comes with a Java wrapper allowing for an easy integration with any Java-based solution."
Datalog -> Gremlin: It shouldn't be too hard to implement Datalog on top of the Gremlin Graph Virtual Machine so that Datalog compiles down to Gremlin bytecode -- SPARQL and SQL implementations already exist -- and running Datalog on the GVM would allow you to run Datalog on any datastore Apache Tinkerpop supports (all the graph DBs, HBase, Cassandra...):
