Clojure has many free IDEs. Many people currently use Emacs w/CIDER, Atom w/Chlorine, Visual Studio w/Calva, Vim w/Fireplace, etc. For that matter, Cursive also has a free non-commercial edition.
As an aside, I'm starting to become a fan of Kotlin for backends (with some Clojure sprinkled in where it offers a big advantage), and Clojurescript (re-frame) for the frontend (because it offers a big win over javascript there). I've taken a step back from full Clojure for everything, being that I have to work with others who aren't as in to "alternative" languages as I am.
Datomic is something I probably won't mess with until (and if) it becomes open source.
Kotlin is great because it's the closest thing to a general-purpose Java replacement I've seen. The interop support between Kotlin and Java is outstanding.
Wishing you and your team many congratulations and kudos on this occasion.