[rspeer]

FWIW, I should mention that I have tried one DB that seems to qualify as a graph database, in that it actually does seem to import and traverse edges efficiently, which is Blazegraph. You tend to have to search past several other things calling themselves graph DBs to find that one.

(But I'm a bit afraid of using it. Any armchair lawyers want to tell me if code that uses a GPL database has to be GPLed itself?)

[jerven]

Don't worry about the GPL part, e.g. see MySQL as a GPL database in wide use.

As long as you access blazegraph via the sparql or tinkerpop interfaces you will clearly be fine.

[dingfeng_quek]

The capabilities and performance of graph databases do differ, and many aren't cheap, nor well known, so if you need one, you'll need to shop around.

Btw, Neo4J is definitely a graph database, although it might not be what you need.