MS haven't publicised it (for obvious reasons), but it seems to be legal.
Paul Thurrott wrote about it on WindowsITPro -
http://www.windowsitpro.com/Article/...5011.html?Ad=1 - and since he is the ultimate MS shill, who wouldn't pass wind without MSs' approval, it's likely legit.
See also -
http://www.theinquirer.net/default.aspx?article=37366
But I don't see many reasons, apart from masochism, for installing this expensive, buggy, bloated, DRM-ridden piece of beta software.