GCHQ/Gaffer: A large-scale entity and relation database

For those who are unfamiliar, GCHQ is the UKs signal intelligence and security agency, similar to the NSA. They have open-sourced Gaffer, a graph database framework which provides fast queries across a large number of nodes and vertices.

https://en.wikipedia.org/wiki/Government_Communications_Head...

> Storage of arbitrary Java objects on the nodes and edges

Seems like a very strange choice instead of something a bit more cross platform.