I wasn't aware that Heroku currently supported anything other than Ruby or node.js, and after looking through their site I can't see anything about Clojure or the JVM either. Does it support JVM languages now?
The Celadon Cedar stack has "undocumented" support for leiningen projects (Clojure). I'm not sure about anything else though... That being said, a big selling point of the new architecture is that they should be able to add new languages/frameworks fairly easily, so maybe we'll see some other JVM languages show up.