You become a MSDN member by buying a supscription. When you are a member they give you "cool stuff" for free. The rules for longhorn are a bunch of copyright stuff.
In short Windows Codename Longhorn is still under patiant by Microsoft and any images could give away trade techniques. Basically Microsoft calls copyright on all longhorn images till it is pubically released but I am also aware that Microsoft does give permission to certian people to show off the images in demos and via other meetings. But there are a number of "illegal" photos out there from Longhorn users that break this contract.
In short Windows Codename Longhorn is still under patiant by Microsoft and any images could give away trade techniques. Basically Microsoft calls copyright on all longhorn images till it is pubically released but I am also aware that Microsoft does give permission to certian people to show off the images in demos and via other meetings. But there are a number of "illegal" photos out there from Longhorn users that break this contract.