The Windows 8.1 Licensing Guide from Microsoft is updated for Windows per User. This is a veritable treasure trove of information! Use it to find out about the new Windows SA per User Add-on and Full USLs, as well as their VDA counterparts.
There’s information on the retirement of the Companion Subscription Licence and how MDOP now extends across multiple devices if Windows is licensed by user.
You’ll also find the downgrade rights for both device and user Windows VL licences, and a useful table showing the SKU availability by VL program. Get this great document here: http://bit.ly/19WbhCI.