There are a few good reasons as to why it might be a good idea for Apple to market Marklar.
1. With the advent of the Dept. of Homeland Security, Microsoft has openly supported the new division of the government, working hand-in-hand with them to make it easier to spy on the publics' computers. Since 85-90% of computer users in the US are on PC's, that's a large percentage. With Microsoft's help, the DHS can access networks through backdoors, and, whether you like it or not, pry into your private life. Because Apple has no such agreement with the government on this issue, security cannot be compromised. Therefore, with OSX - based on a Unix shell - consumers can safely use their computers without fear of invasion of their privacy. More and more PC users are showing their concern about this - it seems that Marklar may be their answer.
2. More software companies will be able to write for OSX - giving Mac users a boost in applications (and, dare I say,
games).
3. OSX is far more stable than its XP counterpart.
4. Apple can truly make a fortune from this - look at Microsoft. If Mr. Gates can become a multi-billionaire from an operating system, then Apple is bound to profit from it - of course, getting more money for its R&D division to make lots more yummy products...
5. Apple is already a well-respected hardware and software manufacturer in their own right. If they released Marklar, they would be in a win-win situation - if it failed, they wouldn't have lost out on the large market share they already have. If it suceeded, then you would more than likely see the demise of Microsoft's dominance in the market.
6. Because of the Megahertz gap (a bit of a myth anyway, but extremely psychological to the company, and influential to the masses), Apple will recapture its dominance in the market by using Marklar, thanks to faster Intel & AMD processors.
I'm sure there are other reasons. But the ones mentioned here are definitely food-for-thought...
