Every few months without fail there's another call for Microsoft to release Windows as an open source platform. This time around it's in the pages of the Wall Street Journal. The easy interpretation: it's a sign the idea has reached critical mass. My take: it's pipe dreaming.

I've talked before about why an open source version of Windows won't happen, but here's a quick rundown of the basic reasons, along with some updated observations.

Patents. It's no secret that Microsoft makes use of plenty of third-party patents within Windows. Ditching each one of them, or finding acceptable substitute code, would make Sun's efforts to open Java look downright pedestrian. I'd wager that's effort they'd be happier to spend somewhere else. [Addendum: This should also include copyright as well; my mistake for not mentioning it explicitly. Patent ≠ copyright, although they share some of the same effects on the way code is used.]

Corporate culture. Let's face it -- as long as people like Steve Ballmer are in charge at Microsoft, there's only going to be so much open source over there. They may host open source on Windows (as Sam Ramji has been elated to point out), but making Windows itself open source is not in the cards -- not as long as they have an office in Redmond with their name on the door, anyway.

Business model. Microsoft makes its dosh by selling access to the Windows APIs as a platform, and also by selling applications to make use of those APIs. Many of their shareholders, I'm sure, don't think of open source as an inevitable destination for software and wouldn't take kindly to what they see as an act of self-sabotage.  (Especially if they're reading articles like this to get their clues about what open source is.)

The real motive. This is something that's come to mind most recently. Do people want open source (transparent, not-proprietary) Windows or free (no-cost) Windows? Is it about clarity of code, or staying afloat on the rising tide of increasingly competitive Linux distributions? These are not interchangeable, although there is overlap.

With odds like these, who's betting? Not me. I could sooner see a desktop Linux distribution eating into Windows the way Firefox glommed something like 20% to 30% of the browser market share from IE. That kind of competition makes more sense on all fronts.