Makes even less sense to me, then.

Redis is less than a year old. I doubt it was a serious contender when Twitter started building their own solution.

Well, the data model seems very similar to Redis' from first glances [1], but FlockDB certainly seems to have completely different durability characteristics. So even if they started anew today they may end up building their own.

1] Which would make FlockDB less a graph db and more a key-value store with social network semantics for the values.

-EE [http://neo4j.org]

Redis is a bit more than a year old. And it's been tagged 1.0 last september. I doubt that that the FlockDB project is much older than that.