A change to the licensing agreement for Apple's OS X Leopard Server will allow users to run virtual machines on Apple hardware for the first time, industry players say.

Virtualization vendors Parallels and VMware are reporting that the revised license agreement for Apple's Leopard Server permits users to virtualize Leopard environments.

Before Mac OS X Leopard shipped, the license agreement for Apple's server software read: "This License allows you to install and use one copy of the Mac OS X Server software (the "Mac OS X Server Software") on a single Apple-labeled computer at a time."

Since Mac OS X Leopard shipped, Apple amended the license agreement to read:

"This License allows you to install and use one copy of the Mac OS X Server software (the "Mac OS X Server Software") on a single Apple-labeled computer. You may also install and use other copies of Mac OS X Server Software on the same Apple-labeled computer, provided that you acquire an individual and valid license from Apple for each of these other copies of Mac OS X Server Software."

This change to the software license agreement was discovered by David Schroeder, a systems engineer at the University of Wisconsin-Madison. Schroeder posted his finding to the MacEnterprise.org mailing list.

The licensing change applies only to the Server version of Mac OS X.

Parallels and VMware -- which provide software for virtualizing physical Macintosh machines -- are each expected to take advantage of the new virtualization capabilities of Mac OS X Leopard Server and are working with Apple to do so.

"We've already begun the steps necessary to technically enable this new policy and Leopard Server is an important part of our Parallels Server road map," says Bill Baker, director of corporate communications for Parallels. "We know from many of you that the 'Holy Grail' of X Servers is to run multiple, isolated, near-native instances of OS X Server on the same box, at the same time."

Parallels expects to offer the capabilities in the next several months, according to a blog posted by Baker.