Apple has altered the software license for its Mac OS X Server, allowing its OS to run in a virtual machine for the first time.

While the license doesn't go so far as permitting server side administrators to install OS X on any equipment other than that made by Apple, it does open the doors just enought to nourish virtualisation developers such as Parallels and VMWare to begin to test the water of running the OS in a virtual way.

Apple’s new software license agreement included with Mac OS X 10.5 Leopard reads: "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.”

Software to enable the installation of the Leopard Server within a virtual machine isn't available yet, but it's expected that Parallels and VMWare will introduce such solutions soon.

The move is a boon for operators, as it will enable them to have multiple virtual servers running on one Xserve, for example, leading to cost and electricity demand reductions for multi-server set-ups.