Jeff Moden (8/5/2014)
From my understanding, it's not actually free. It should be the Developer's Edition and each chair should have a license for it. In quantity, they can be as low as 30 bucks from a good MS authorized dealer.
I investigated this the other day yep Developer editions aren't free but minimal cost - plus you will need to go through an authorised dealer. (At least in the UK) Not sure whether you get things like the Stream insight framework with that either.