[ndr]

If you like lisp, and especially clojure, check out babashka[0]. This my first attempt but I bet you can do something nicer even if you keep forcing yourself to stay into a single pipe command.

  cat repos.json | bb -e ' (->> (-> *in* slurp (json/parse-string true))
                                (group-by #(-> % :license :key))
                                (map #(-> {:license (key %)
                                           :count (-> % val count)}))
                                json/generate-string
                                println)'

[0] https://babashka.org/