open stack ? There is no such thing as free sauce in z-wave.
Sign the NDA , use the precompiled libraries and off you go. the z-wave protocol is closed and secret.
Even witht he NDA signed they will not disclose how the routing etc works. you get a precompiled library and an API. the z-wave stack is not available in source form.
It contains a number of features not found in zigbee (where everyone just farts around and doesn't give a rats ass about interoperability with someone else's products ).
Your product needs approval to get it on the market. simply to guarantee it will play nice with the other devices .
Like i said : i have a z-wave system in my house. Setup is real simple. Click the 'learn' button on the dongle , press the button on the device and they are now paired. the system is a mesh network that is self learning and self routing. i can send commands from a master to a slave (actuator device) , or 'pair' a controller to a slave device. The beauty of z-wave is that there is no master controller required. Most domotics system bank on a central controller. if that controller dies, crashes, explodes or whatever the entire system stops working. Z-wave doesnt have that problem. if a node dies , only that node is dead. the rest keeps functioning as intended.
oh, and z-wave is not french ( i don;t know where you got that ...) it comes from the scandinavian countries. denmark i believe )