Actually, it can be (and is) used as a general-purpose build tool. I'm using it in some otherwise Java-only projects, and — who knows — it might even start getting some love from Scala hackers:
Once jark (a persistent Clojure/JVM backend @ http://icylisper.in/jark/) is made to work well with Leiningen, then the combination might be a reasonable replacement for sbt.
https://github.com/technomancy/lein-scalac
Once jark (a persistent Clojure/JVM backend @ http://icylisper.in/jark/) is made to work well with Leiningen, then the combination might be a reasonable replacement for sbt.