Stuart Halloway said "Datomic is not and will not be open source" in the latest defn podcast, so don't hold your breath. Hopefully they change their mind.
They seem to be focused on a cloud (managed?) solution offering at the moment.
It's not helping clojure grow as much as it could though and it's a bit a chicken/egg problem, more clojure users could be more datomic users and vis-versa.
I would only make a closed-source solution a centerpiece of my business if:
* The thing is known to work for a number of other people, and uniquely solves my urgent problem, while no open solution can't do anything comparable. This is probably the Datomic niche.
* The thing was around for ages, and is a cash cow of a major and reliable software maker, and is also significantly better than open software in some important area. This is how MS or IBM sell their databases; Datomic doesn't have nearly enough mindshare to compete here.
* I'm hastily building an MVP that I plan to scrap anyway when the growth hits / the startup is acquired. Datomic is likely too expensive for that.
By necessity, the first case holds for a small number of businesses.
I've been considering trying to get up to speed with Mentat[0], which is a Mozilla project to create a Datomic-like layer over SQLite for desktop applications, and help out with that or even try to start a full open source clone of Datomic, though probably won't happen for a good while due to real life happening.
It's got so many good ideas and it sucks to see them go to waste in a proprietary database where basically nobody gets to use them.
What if it's unobviously not possible?
edit: found it https://soundcloud.com/defn-771544745/23-the-right-honourabl...