Clojure

Clerk: Interactive notebooks done right
Lots of Datalog engines, mostly following Datomic
Morse: Graphical, interactive tool for browsing and inspecting Clojure data
Rama: Backend platform written in Clojure
application.garden: Batteries-included web app hosting (from the makers of Clerk)
GitHub - sixthnormal/clj-3df: Clojure(Script) client for Declarative Dataflow.
vvvvalvalval/scope-capture: Project your Clojure(Script) REPL into the same context as your code when it ran
Kira McLean | Building A Fast Command Line App With Clojure
GitHub - mentat-collective/emmy: The Emmy Computer Algebra System.

Shortcut | Project Management for Software Teams: Home of Alessandra Sierra (2017)

Clojure is licensed under the Eclipse Public Licence (formerly the Common Public Licence, but same idea).
Why, particularly as opposed to the GPL or something GPL-compatible? Hickey likes the EPL definition of "derivative" better. If you combine the Clojure compiler with separate code under some other licence, the combined non-derivative work doesn't need to be distributed under EPL. GPL does not make this combination/derivative distinction, and would require the combination to be GPLed.
Hickey doesn't want to be embrace-extend-extinguished, but he also, on principle, doesn't want to force a licence on anyone who isn't directly changing Clojure itself.
Hickey also, personally, can't use GPL for his own work, and doesn't want to see contributions made to Clojure under GPL that he can't use himself (so no GPL even as a dual licence). Selfish, but fair enough
See https://www.juxt.pro/blog/prefer-mit