Well, Clojure has hot-swapping code for source Lisp files, but you can't load compiled libraries (Java, Clojure, Scala, whatever) into the running JVM, as there

Well, Clojure has hot-swapping code for source Lisp files, but you can't load compiled libraries (Java, Clojure, Scala, whatever) into the running JVM, as there's no way to dynamically add JARs. This is quite a limit, especially in production scenarios.