Calling Clojure from Java is ugly, but calling Clojure from JRuby is quite pleasant, and I'm pretty sure a nice Clojure library could be written for calling JRu

Calling Clojure from Java is ugly, but calling Clojure from JRuby is quite pleasant, and I'm pretty sure a nice Clojure library could be written for calling JRuby from Clojure. Calling Clojure from Java is difficult because Java is inflexible more than some inherent weakness in the "bootstrap on a host VM" strategy. I've written a library to call Clojure from JRuby. It's about 100 lines, and took me an afternoon. I assume the situation is similar all high level JVM languages. Given all the above, I agree that the JVM languages will fragment somewhat, but to a lesser degree than you seem to think. If there are any really killer app libraries in one language, it won't be too hard to integrate them into the other languages.