It’s technically called Microsoft Hyper-V Server 2008 R2. That’s why I call it the free edition of Hyper-V.
What you get is an ISO that will install Windows Server 2008 R2 Core edition running Hyper-V. The license for that is 100% free. If you install a guest running Windows you will need a license for the guest, but if all you did was install Linux guests you could have a 100% licensing cost free environment.
Realistically if you are a windows shop you are going to be buying datacenter licenses for the physical CPU’s to cover an unlimited number of guests. And if you are not a windows shop you are not going to be using Hyper-V for no other reason than it does not have great Linux support yet. But if you just want to look at Hyper-V or use it in a lab environment this edition of Hyper-V can come in quite handy.
And yes this blog post is mostly here so I can find the download page in the future. If you can find it on your own within five minutes then I am impressed.