VMware dodged a bullet this week, though its escape has more to do with Microsoft's reluctance to give up a dollar of revenue even to make life easier for its customers than to anything VMware has done to secure its own position.

Microsoft, which is a giant in the market for business applications as well as in operating systems and the hypervisors that virtualize them, had the opportunity to coordinate license changes for its software to make the construction and management of virtualized data centers a lot easier.

Today Microsoft announced it has recast the license requirements for 41 server-based applications so the applications can be moved from one virtual server to another within a server farm without any additional license fees.

The central change: the elimination of a 90-day delay on server application licenses. Previously, users could move an application from one virtual server to another, but first they had to license both the old server and the new one, according to Zane Adam, senior director of integrated virtualization in the Server and Tools business at Microsoft.

Applications had to be licensed to the particular server on which they ran, Adam says. The requirement was a holdover from the days before virtualization, when an application had to be licensed to a specific piece of hardware and could only be moved after 90 days. That, presumably, was to keep customers from licensing SQL Server on a four-year-old, one-processor Dell, then shifting it to a 16-processer, 64-core IBM superserver an hour later.

Freeing up an application, especially one like SQL Server, is a real benefit for end-user companies, according to Chris Wolf, analyst with the Burton Group. Many ISVs embed in their own custom-designed applications, for example, so customers wanting to migrate a custom app around a server farm can get hung up on the license for an application they didn't necessarily want, anyway.

License terms that punish customers for moving an application from one VM to another are counterproductive for both vendors and customers, Wolfe says. Virtualization is common enough now that licensing terms favoring virtualization are an absolute requirement for many customers.

Microsoft's new license terms also cover products from any virtualization vendor that has gone through Microsoft's Server Virtualization Validation Program (SVVP), which certifies virtualization solutions for Windows Server 2008 and other Microsoft products.

On Aug. 18, VMware signed an agreement to put its products through SVVP, according to a Microsoft spokesperson. That seems to be that both VMware and Microsoft are cutting things a bit close, considering Microsoft announced the license changes one day later, but what's life without a little brinksmanship?

Cisco, Citrix, Novell, Sun and Virtual Iron signed on to the SVVP long before, by the way; so Microsoft's license changes cover all the major hypervisor suppliers.