Parallels is claiming to be the first virtualisation vendor to support guest virtual machines running Apple's Mac OS X operating system. The feature is currently only supported in its Parallels Server for Mac product, but the move might eventually lead to users being able to run OS X alongside Windows on non-Apple machines.

The company unveiled a beta of its Parallels Server for Mac, Windows and Linux at Apple's 2008 MacWorld Expo in San Francisco, and demonstrated its ability to support Leopard Server running as a guest on a host Mac system.

Apple previously licensed OS X on a single copy per machine basis as well as restricting its use to Apple hardware, but its position was relaxed slightly with the release of the server version of OS X 10.5 Leopard late in 2007.

"It's an Apple licensing change that has allowed this to happen. With Leopard Server, the EULA now says you can run multiple copies on the same machine," said Parallels director of communications, Ben Rudolph.

This license change applies only to Leopard Server, not the desktop client version, and still stipulates that the software can only run on Apple's own hardware. Nevertheless, the move is "a good step in the right direction", according to Rudolph.

Because Apple switched to using Intel chips in its systems, its platform is theoretically capable of running on standard PC hardware. Industry watchers have speculated that many Windows users could be tempted to try out OS X in a virtual machine, and some might even switch if they like what they see.

"They haven't given us any indication of this, but it isn't out of the realms of possibility down the road," said Rudolph.

Richard Edwards, senior research analyst at Butler Group, agreed. He said that the current licensing move was not greatly significant to most users, but i t showed that Apple was re-considering its position.

"They are beginning to recognise that we live in a virtualised IT world, and rather than put blockers up for those that might consider Apple in their infrastructure, they have started to listen to customer demand," he said.

Edwards said that Apple is unlikely to let OS X run directly on standard PCs because of the support problems this would cause due to the wide variety of hardware out there, while it has control over what goes inside a Mac. However, the ability to run OS X in a virtual machine would be valuable for running different versions of the platform side-by-side for evaluation purposes, and so it seems likely that users will in future be able to do this.

"Apple is thinking about things it never did before – it's a business and has to consider what will help it expand," Edwards added.

The release version of Parallels Server for Mac is due to ship in the middle of 2008.