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."
https://www.cs.ox.ac.uk/isg/tools/RDFox/
Dedalus: Datalog in Time and Space, by Peter Alvaro out of UC Berkeley (note the StrageLoop talk):
https://disorderlylabs.github.io/
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...):
Graph Computing with Apache TinkerPop, by Marko Rodriguez (the creator of Gremlin) https://www.youtube.com/watch?v=tLR-I53Gl9g
A Gremlin Implementation of the Gremlin Traversal Machine http://www.datastax.com/dev/blog/a-gremlin-implementation-of...