You might find this useful:

http://java.sun.com/sfaq/#otherBytes :

Frequently Asked Questions - Java Security

17.If other languages are compiled to Java bytecodes,
   how does that affect the applet security model?

  The verifier is independent of Sun's reference implementation
  of the Java compiler and the high-level specification of the
  Java language. It verifies bytecodes generated by other Java
  compilers. It also verifies bytecodes generated by compiling
  other languages into the bytecode format. Bytecodes imported
  over the net that pass the verifier can be trusted to run on
  the Java virtual machine. In order to pass the verifier,
  bytecodes have to conform to the strict typing, the object
  signatures, the class file format, and the predictability of
  the runtime stack that are all defined by the Java language
  implementation.