Licensing savings were one of the main arguments initially made in favor of application streaming, the first desktop virtualization technology aimed at the enterprise. Vendors like Softricity promised that centralizing applications on a server, instead of installing them on every desktop, would mean fewer required licenses, because apps would need to be licensed only for the number of people actually using them at any given time. That savings pitch fell by the wayside, however, once Softricity was bought by Microsoft.
Streaming still has the potential to save on licensing, but only because it provides greater visibility into who is using which applications, a feature also found in most desktop management software. The problem with license sharing is that apps like Microsoft Office are tied to a particular PC, and licenses aren't easily transferable. Many popular apps are also licensed per user, which is nice for people who want to install a single copy on both a desktop and a laptop, but not so good for companies hoping to save money by consolidating users around a single PC.
Application virtualization makes it possible to use more than one version of an app at a time, but Microsoft Office users must either buy separate licenses for each version or join Microsoft's Software Assurance program, under which customers pay a monthly fee for updates. Microsoft denies that this is software rental, preferring to call it a "time-limited license." Software Assurance helps customers who want to shift from capex to opex, but it can be more expensive in the long run. Still, Microsoft is heavily pushing Software Assurance, with virtualization as an important driver. Its own Microsoft Application Virtualization (formerly SoftGrid) product is available only through Software Assurance, as is Vista Enterprise, the only version of Windows that can legally be run in multiple VMs without buying multiple copies. The license lets users run up to four separate instances of Vista, or previous Windows versions, on each PC.
In the long term, that could be a powerful incentive to upgrade to Vista, especially as virtualization itself can solve many compatibility problems affecting legacy apps. But there are still compatibility issues with newer Windows features, in particular BitLocker encryption and Rights Management Services. Microsoft's licenses prohibit use of either in virtualized environments, as current hypervisors aren't designed to work with the Trusted Computing security model. Back in 2003, Microsoft talked about creating a desktop hypervisor that would support use of advanced features as part of its Palladium road map, but that's on indefinite hiatus.
As with servers, other versions of Windows are licensed to run on only one machine (physical or virtual) at a time. Windows shops that don't want Software Assurance, or Apple customers that want to run virtual Windows, must buy separate licenses for each instance of Vista Business, Vista Ultimate, or Windows XP, an expensive proposition because licenses must be for full copies, not upgrades or OEM versions. The less pricey Home versions of Vista can't legally be run in VMs at all.
COMING TO A DESKTOP NEAR YOU
Because the hardware-assisted virtualization that AMD and Intel are adding to their chips applies across their full lines, regardless of whether the chip is designed for a workstation or server, full VMware-style virtualization soon will become more common on the desktop. Intel's vPro initiative promotes desktop virtualization as a means of helping enterprises keep control of systems: A management or security agent can run in a separate VM from the main OS, immune to malware or configuration changes made by the user.
Rather than enter the management or security markets, Intel is partnering with established vendors, including CA, Check Point, Cisco Systems, LANDesk, Novell, Symantec, and Trend Micro. The original plan was that all would offer management agents running atop Windows CE, which in turn runs on a custom version of the Xen hypervisor alongside the main Windows XP or Vista OS. However, although vPro chips first shipped in September 2006, only Lenovo offers a VM-based agent. According to LANDesk and Symantec, the main reason for the delay is that management vendors are unwilling to pay Microsoft's licensing fees for Windows CE. As an alternative, Intel in May announced a partnership with Red Hat to replace Windows CE with Linux, with likely availability in mid-2008.
There's even better news for Windows desktop users switching to multicore CPUs: Microsoft's per-socket licensing applies to clients as well as servers, so all versions of Windows XP and Vista are able to use the full capabilities of quad-core and future processors. But if you have power users who require two physical CPUs, be careful, especially if upgrading to Vista. Whereas XP Pro supports two sockets, all versions of Vista except Ultimate are limited to one.
Software Licenses: Take Your Pick