Customers are using virtualization technologies more and more for a variety of reasons – as part of server consolidations, for test and development, to create a more agile infrastructure that allows them to move workloads from machine to machine regardless of hardware, to establish better business continuity and to reduce downtime.We wanted our licensing to allow customers to embrace virtualization benefits and eliminate any potential barriers. As a result, we have devised licensing policies that we feel best reflects how our customers want to use this virtualization technology.
http://www.computerworld.com/softwaretopics/os/windows/story/0,10801,105271,00.html
http://www.microsoft.com/presspass/features/2005/oct05/10-10virtualizationlicensing.mspx