Microsoft Loosens The Reins On Server Virtualization Technology

Microsoft wants its partners and customers to know they won't have to pay licensing fees or risk legal action for using a key application programming interface for Viridian, the vendor's eagerly awaited server virtualization technology.

On Wednesday, Microsoft added the hypercall API for the Viridian hypervisor to the Open Specification Promise, a designation aimed at encouraging third party development which applies to a handful of the software giant's Web services, security, Office XML, robotics, and virtualization technologies.

Microsoft believes that having the hypercall API under the OSP umbrella will spur organizations to extend and integrate their offerings with Windows Server 2008 and Viridian.

Now that the hypercall API is covered by the OSP, "any individual or organization is free to implement, commercialize and modify Microsoft's virtualization format technology for free, now and forever," according to a Microsoft spokesperson.

Simon Crosby, chief technology officer and co-founder of Xensource, now part of Citrix, says today's move will help to ensure compatibility between virtual machines created on XenServer and Windows server virtualization.

"Viridian is a very valid implementation of the Xen hypervisor, and this will allow us to have a product that essentially extends the dynamic virtual service layer and gets Xensource into the Viridian footprint," said Crosby.

Windows Server 2008 is currently in its third beta, and Microsoft says plans are to release it to manufacturing sometime in Q1. The launch of the Viridian hypervisor, which will give Microsoft an answer to entrenched virtualization offerings like VMware's ESX Server, will come about six months later.

Microsoft currently offers a line of virtualization products that includes: Virtual PC and Virtual Server 2005 for desktop and entry-level server virtualization; SoftGrid for application virtualization; and terminal services for the presentation level.