Jikes RVM

Does anyone know why we're not using the Jikes RVM? Its a JVM written in Java. It is being actively developed and is very fast. The source-code is licenced under the CPL I think. Surely it would be compatible with JNode's GPL at a class-level. What do people think about adapting JNode so it can run with the Jikes RVM as an option? I do think that the burden of developing an OS and a VM is a lot. What are peoples thoughts?