Microsoft made a series of announcements on Monday regarding virtualization, including the acquisition of Calista Technologies. Buried in the announcement was a relaxation of the license terms for use of Vista Home Basic and Vista Home Premium in a virtualization environment, for example, Parallels Desktop or VMware Fusion on a Mac.

The applicable part of the press release said:

"Increased licensing flexibility with Windows Vista. ... For consumers, Windows Vista Home Basic and Windows Vista Home Premium are now licensed for use in a virtual machine environment, and the updated end-user license agreement is available at http://www.microsoft.com/about/legal/useterms/default.aspx."

When Vista first shipped, Microsoft required customers to buy a business version of Vista in order to install it in a virtualized environment, an expensive proposition for most individual users. Microsoft did not cite any reason for the change, but itis known that lobbying from Parallels and perhaps VMware occurred, and that may have caused Microsoft to alter the licensing terms.