Today is great day for z-wave community, the whole SDK for Devices and Gateways, and complete Z-Wave documentation can be free downloaded from silabs.com website (all you need is to create an account on Silabs page)
Please login or register to see this link.
This is from developer / home developer point of view great things, but there is more. One can download as well all the tools:
(afaik from Silabs legal point on of view - see Legal and FAQ Silabs webpage - should be ok