Question about Heat and PT11 HDX.

This Heat thang is kind of confusing. Does it work with Mac PT11 HDX? Also if I buy a license where do you download it from? The link on the Avid site always seems to revolve me around to a page that looks like you have to do a new install of PT to get Heat. I don't really want to do that. Anyway, any help would be appreciated. Here's a link to it on ebay, would this work with my system:
http://ift.tt/1EmaduD