Volume customers can now install Microsoft's desktop applications as many times as they want on each device for which the application is licensed. The change, announced in a new release of product use rights for volume customers, paves the way for wider use of virtual machines (VMs) on desktop computers and will make it much easier for organizations to migrate to new versions by using VMs.

Virtualization Licensing Evolving

Microsoft has been evolving its volume licensing rules to incorporate VMs since early 2006, but most of the licensing liberalization applied to server applications, such as the decision in 2006 to require licenses only for running instances of server applications, rather than installed instances. (For a broad review of virtualization and applicable licensing, see "Virtualization Licensing Adapts to New Challenges".)

For many years, Microsoft permitted customers to install a second copy of a desktop application, such as Office, on a portable device and on a network, as long as it was used primarily by the same person to whom the initial desktop license was assigned. In 2006, the company amended that rule to permit installation of that second copy either on a portable device or on a VM running on the licensed device—but not both. Another copy could be installed on a network device, such as a blade PC or Windows Terminal Server, for the use of the primary user of the license.

These rights also included the right to use a copy of a previous version of the software rather than the current version.

New Rules—Unlimited Installs

In Apr. 2007, Microsoft further amended its product use rights for desktop applications to permit installation of any number of copies of the software, or a previous version, on the licensed device. Rules regarding installation on a portable and network device remain unchanged.

The new rules will make it easier for organizations that want to use VMs on desktop computers, particularly when they are combined with relaxed OS virtualization rules introduced with Windows Vista for customers with Software Assurance (SA). Those rules permit organizations with access to Vista Enterprise Edition, which is available only to customers with SA, to install up to four additional copies of the OS (or an earlier version) in VMs on the same device. (Without Vista Enterprise, customers will need to purchase an additional OS license for each VM.)

The new rules will be most useful to organizations that need to migrate documents, applications, and users from earlier OS and application versions, such as Office 2003 running on Windows XP to Office 2007 running on Vista. They can create VMs running the older OS and applications, and users can switch between newer and older versions of the software without requiring additional Office licenses (although additional OS licenses may be required in some cases).

The new rules also allow organizations to run multiple versions of software side by side, and when that solution is feasible, it will generally deliver better performance than running one version in a VM. However, some applications cannot run side by side on the same machine: a new version may forcibly upgrade any earlier versions or may update data formats irreversibly. VMs are better for isolating multiple installations, permitting then to run simultaneously without conflict.

Product use rights can be downloaded from www.microsoft.com/licensing.