An emulator that allows Apple's OS X to run on Windows-based PCs has its critics, writes Robin O'Brien Lynch.

The introduction last week of CherryOS, an emulator that allows the installation of Apple's OS X operating system on a PC running Windows XP, seemed to be perfectly timed.

With the success of the iPod and the Mac mini, niche specialist Apple has made inroads into the mass computer market for the first time since it lost its position as the world's leading personal computer maker during the 1980s - and the advantages of OS X are widely appreciated.

Meanwhile, Microsoft's reputation is suffering as more and more Windows users find that viruses, worms and spyware are taking over their PCs and the introduction of Longhorn, Microsoft's new operating system, is delayed once again.

However, Microsoft's strong point will always be that people are reluctant to change from an operating system and the related software that they have grown up with - let alone go out and buy a new computer to run it on.

There may now be a way around that problem. The maker of CherryOS, Hawaii-based software firm Maui Xstream, claims that its product enables Windows users to run Panther, the latest version of Apple's OS X.

"In addition, you will be able to use many of the day-to-day applications, such as Safari and Apple's Mail," the company's website, www.mxsinc.com, claims. "It's perfect for learning a new environment, expanding your PC's capabilities or finalising your purchase decision [ of an Apple computer]."

The product also benefited from two postponed releases last year and the resultant hype.

CherryOS costs $50 (€37.38) with the option of a free trial download. On top of that, a copy of Panther currently retails at about $129.

The developers claim that the emulator should run at about 80 per cent of the host PC, which would be a significant improvement on any earlier attempts at running OS X on PCs.

However, the Cherry project has been dogged by controversy since it was first announced.

People were suspicious as to how a little-known Hawaii-based outfit, which had previously restricted its operations to video-streaming software, could suddenly do something that had evaded much larger firms.

There was another difficulty: in between Cherry and Apple there was Pear.

PearPC is an open-source, free-to-use emulator that has been available since May. It is still under development by a team of volunteers but has built up a dedicated fan base despite its experimental status.

On its introduction, it came with the warning: "Please note that this is an experimental program not meant for productive use. There are still unimplemented instructions, mysterious bugs and missing features. Don't use it on important data: it will destroy them sooner or later!

"However, if you are brave enough to try it out, fetch one of the builds or the source. Don't forget to read the documentation, it will save you hours of frustration! And please don't whine if it doesn't work for you, but fixes the bugs."

Like all open-source software, users with a knowledge of programming are invited to try the product and see how can they improve on it.

Now on its fifth release, Pear still has a long way to go before all the bugs, errors and problems are resolved. It is released under the General Public Licence (GPL), which means it is free to download and use, but any modified releases must also be available free to the public.

Under these conditions, it is a breach of the licence to sell copies of any software released under the GPL, and this is exactly what many people have accused Maui Xstream of doing.

The GPL's definition of "free" is not related to price but freedom, and the open-source community do not take kindly to the suggestion that their work is being hijacked for corporate gain.

The accusations are that CherryOS is merely the source code for PearPC, taken from its open-source origins, modified and sold for a profit.

Dave Schroeder, a senior systems engineer at the University of Wisconsin-Madison, was distinctly unimpressed.

"I'm surprised at the gall of some people," he said. "This is obviously PearPC. When you examine the executables, it's still got so many identical strings that aren't just generic. CherryOS is still using significant amounts, if not all, of PearPC's code as the emulation engine."

Schroeder also highlighted another potential difficulty for Maui Xstream. Under Apple's licensing agreement, OS X can only be run on one Apple-branded computer at one time.

"PearPC does not promote or market itself as a tool to exclusively run Mac OS X," he said.

"CherryOS, on the other hand, is a commercial product that is specifically marketed to people for running Mac OS X on Windows systems, which is a clear violation of Mac OS X's licence agreement."

Whether or not Apple assembles an army of lawyers before Maui Xstream goes ahead with plans to release a version of Cherry that will allow PCs to run OS X without Windows XP, the question for consumers remains: does it work?

The natural concern would be that if the download stage passes without crashing, the product may still be clunky and irritatingly slow. The only way to find out is to download the free trial from www.cherryos.com, but a spokeswoman for the company, Karol McGuire, claims that performance depends on the individual processor.

"How CherryOS performs on an individual user system is dictated by the host system," she said. A processor that has inadequate space on the hard drive or that runs at less than optimum operating speeds will not allow CherryOS to perform as designed.

"There are hundreds of PC versions on the market today; our experience is that about 70 per cent of PC users are able to successfully install and use CherryOS. That compatibility will increase as upgrades are implemented.

"In the meantime, we encourage all prospective buyers to download and test the complete 'free for five days' version of CherryOS available on our website."

Maui Xstream said that it was working on updates that would improve compatibility and increase that 70 per cent figure.

As to claims that Cherry is just a rip-off of Pear, McGuire said: "Absolutely not. Certain generic code strings and screen verbiage used in Pear PC are also used in CherryOS. They are not proprietary to the Pear PC product.

"For example, Pear tops out at G3 emulation and CherryOS is the only stable G4 emulator on the market today. CherryOS uses multithreading architecture for speed and ease of use.

"Pear employs a step-by-step approach; CherryOS features a shared-drive emulator, a drag-and-drop option allows you to connect the Windows drive to a Mac environment and CherryOS is the only emulator to support sound.

"There are considerable differences between the two products: Both products emulate the Apple operating system but the similarity ends there," she added.