The progress has been a bit slow lately with the z-wave stuff... But I have bought some stuff and I am actually using a Z-Wave wall switch connected to OpenNethome in my apartment, even though the implementation is a bit prototypish.
I cannot make any promises yet, but it will probably work to first use z-way and then OpenNetHome, but you will not be able to run them at the same time, you will sort of have to "migrate" to OpenNetHome.