These three products are an $850 value that can be yours for nothing. Signing up doesn't even require a credit card or address, just a username and email. Once you do that, check out with the three products (making sure they still say $0 for the charge) and they're yours. The product codes sit in your account and are emailed to you and the PC and Mac downloads will be waiting for you on the site.
DAZ 3D has a history of giving away their products for free like this, as they can still generate a profit from content sold through its web-based marketplace. I think they probably sell stuff like figures, models, set pieces, etc.
So go check it out. Make sure they are still being offered for free when you visit and enjoy the free design software.