@Richard
I read that it's free for use in DS, but if you want to use the outrput commercially, then you still have to pay for an iRay licence.  I'm pretty sure it was iRay, I think it was in that massive thread on DAZ where I read it when they first released it.  If not, I must be thinking of something else, but I can't think what!

Anyway, that's good to hear, thanks for the heads-up :-)