As far as contributions, as we transition our product to OpenJDK, we will eventually contribute all the GPL code involved, but we expect to actually add contributions well before that. So, there are specific areas of improvements and enhancements to the Hotspot, mostly to the VM itself, that we have done that we would like to see just put upstream and for everybody to benefit from. It would help us reduce the amount of integration we have to do when we take a new release with bug fixes and put them in. For example, anything from supporting a fully 64 bit clean implementation without warnings around the board, just clean-ups and things like that are there, to enhancements to locking, addition of things like read barriers across the board, and various enhancements to do with the thread model and other things in the JVM that we've put in and we think would be useful for the community as a whole.
Gil Tene, Azul Systems' CTO in an interview with InfoQ.