For the first time, Apple is allowing customers to run multiple copies of an Apple operating system in virtual machines. Apple's software license agreement for Mac OS X Server 10.5 (Leopard Server) allows users to run multiple copies on one Mac, provided that they pay for each copy.

The agreement states "You may also install and use other copies of Mac OS X Server Software on the same Apple-labeled computer," as long as you have a license for each co090607apy.

Apple is not extending the same permission to the Leopard workstation, however. That software license agreement lacks the sentence about installing and using other copies on one Mac.

Until now, Apple customers were missing out on the growing trend of server virtualization, which can cut down on the number of hardware servers required, save energy, and consolidate management and configuration tasks. Runnign servers is virtual machines is also useful for testing.

The Leopard Server license agreement also does not, however, permit users run Leopard Server on non-Apple hardware, which means that customers won't be able to run it using one of several hypervisors now available. (A hypervisor is a small bit of software that allocates hardware resources dynamically to multiple virtual machines.)

One could run multiple copies of Leopard Server using Parallels Desktop and VMware Fusion. The two companies have said in the past that it would not be technically difficult to enable their software to run Mac OS X, but they have not done so because of Apple's prohibition.

At VMworld in San Francisco this past September a company called Moka5 demonstrated Mac OS X running in a virtual machine on a Windows XP PC last September at VMworld in San Francisco. The company's Moka5 Engine is software that creates virtual machines and deploys them on multiple PCs over a network. Apple's software licensing agreements forbid deploying Leopard Server and workstation in this way.