Actually, jails are pretty easy, and I was one of the first people to utilize them heavily many years ago ... but the FreeNAS implementation is more complicated because of the base system constraints.
Figuring out the requirements for what Virtualbox needs in order to make that USB device accessible might be a little crappy. There's always the alternative of just acquiring some small low power dedicated PC-box to handle this instead.
Like a raspberry pi. That's what I'm using to control the home domotics. There is a ton of info on working with domotics and different protocols on the pi. I which my stuff used zwave (mine uses Enocean), would have made my life (well, that life experience at least) al lot easier.
The idea of buying a small low power dedicated box, like the raspberry pi, was something that I would really see as a waste since I have my FreeNAS machine always up and running with enough memory and power. Also knowing it has the possibilities to run the software and me not being able to get it running was something I didn't like. :)
So going down the virtualbox way seemed to be quite easy. I installed Debian 7.8, the OS that most of the raspberry pies are running with the domoticz software, and then compiled Open-ZWave and Domoticz. Then I followed the guide from
this thread to get the USB passthrough working. When I was done all worked immediately. So now I have it all running in a environment which is really close to what around 90% of the users of domoticz use on their raspberry pies.
Thanks for all the suggestions and advice!