Server virtualization is a red-hot technology destined for deployment in most enterprises, but IT shops are paying a steep price because some software vendors have adopted licensing and support policies that penalize companies for running applications on virtual machines rather than physical ones, a new report from the Burton Group says.

"There is an abundance of user angst and uncertainty surrounding the licensing and support of applications running on x86 virtualized environments," Burton Group analyst Chris Wolf writes.

Some vendors simply won't support their applications when they run inside VMs, states the Burton Group report, titled "Virtualization Licensing and Support Lethargy: Curing the Disease that Stalls Virtualization Adoption."

But software providers can make life difficult and more expensive for customers even without such an all-or-nothing approach. Vendors sometimes will support applications on virtual servers only if they run on certain platforms, typically VMware ESX Server, Wolf writes. Sometimes they tie licenses to hardware components that may change as VMs relocate from one physical host to another, or penalize customers for maintaining offline copies of virtual machines for disaster-recovery purposes.

Frustrated customers "often deal with software vendor support by either 'accidentally' failing to disclose that an application is running in a virtual machine (VM) or by cloning the VM to a physical server before calling support," Wolf writes.

The Burton Group recommends that vendors develop common license management standards, and remove all restrictions on VM mobility in product licensing. The analyst firm gives high marks to some vendors, such as SAP, which has employed virtualization architects to help write policies "fully compatible with modern virtualization architectures."

The 51-page report reviews vendor policies in three categories: server operating systems, management applications, and client-server applications or middleware. 

Server operating system licensing policies are "generally virtualization-friendly" with a few exceptions, while there are more problems on the application front, with independent software vendors often binding application licenses to physical server hardware.