I have just recently discovered Project Sumatra, which aims to bring the JVM to the graphics card. From their webpage this includes a custom compiler (called Rootbeer) for Java.
This is all good news, however, I would like to hear from someone with more knowledge about the project internals if this means that project Sumatra applies to other JVM languages as well? Will it be possible to make Aparapi calls from Scala or Clojure directly? Or will you have to develop some core functionality in Java and then access that via other JVM languages?
AFAIK Rootbeer (a university project) and Aparapi (an AMD based project) are unrelated, so you may haved missed something here.
Regarding Aparapi itself it states in its Wiki that it won’t work with Scale/Closure etc. or in fact with anything except pure Java, since it depends on patterns used by JDK’s javac to properly analyse bytecode. It also requires you to extend its Kernel class to be able to convert the bytecode into OpenCL and execute it in GPU. So it looks like you would use one or another.
Back to your question: based on all this you would have to develop in Java and call it from other JVM languages.