[Skinney]

Part of the reason is that it's been a commercial database until recently. I also think it hasn't helped that it's closely associated with Clojure (for natural reasons), which might make Java developers turn away from it.

It's a shame, though. Datomic is a marvel.

[kragen]

quite aside from whether or not it's 'commercial', it's proprietary

[amelius]

Yeah, the cost is the biggest reason probably. There's probably a lot of in-house developed Datomic clones out there (I know one, that was developed even before Datomic was a thing).