Who knew that Apple's latest version of Mac OS X was knitted together from enough open-source software to give Linux a run for its money?That became apparent the other day when Apple released Darwin 9.0, which is the source code behind Leopard.

True, there's no earthshaking news here. Apple has been publicly disclosing the source code behind OS X for years, and the Mac maker has long touted the inclusion of open-source in earlier versions of OS X. Here's how Apple explains it on its Developer Connection page:

Still, it's astounding when you count up the number of open-source modules included in Leopard. The full list is posted here. For many of these, you can download an archive which includes deep technical information and/or source code.

When you think about it, an engineer or student with time on his or her hands could do a couple of things with this stuff. Purely for the challenge, they could construct their own "version" or twist on Mac OS X. (True, they probably wouldn't be able to get all the way there, because by no means is all of OS X public. Also, they wouldn't be able to promulgate their code, because it wouldn't be properly licensed.)

On the down side, people with malicious intent can use this extensive archive to figure out ways to hack the Mac. The fact that this hasn't happened -- like I said above, Darwin has been available for years -- is a testament to the integrity of the Apple community. More likely, it just means that it's really true that virus writers aim at the far more widely deployed Windows platform.

The third outgrowth of OS X source-code availability should be that applications developers have been better able to get their programs to work cleanly within the ecosystems of Leopard and its predecessors. I'd love to query developers at companies large and small and see if they get any benefit out of this stuff. (Here's an interesting list of OS X applications.)

What's In The Code

Turning from the philosophy back to the software, it's amazing to see both what's available as well as the debt Apple owns to programmers working outside of its own walls.

Take Kerberos, the network-authentication protocol which allows secure communications over a nonsecure network. It was developed by MIT and licensed by the school to Apple. You can get at all technical information on MIT's Web site.

True, enterprising users can get at stuff like Kerberos if they're willing to do a little research. But Apple has made the task much easier by posting all this stuff. While I haven't been bashful in bashing Apple in the past, I have to give the company kudos here. That's doubly true when you contrast Darwin with Microsoft's general historical reluctance to open up Windows source. (Microsoft did agree to license Windows Server source code in 2006.)

More Linux Than Linux?

Delving into Darwin a little deeper put me in mind of some other, less conciliatory thoughts. Apple has helpfully posted a collection of articles explaining some of the other open-source technologies which are either a part of Mac OS X or which work with it.

The list starts with Mach kernel, originally built at Carnegie Mellon University and now the basis for OS X kernel, and goes on from there.

Thus we have the evidence that Apple has obviously figured out how to successfully build on the work of others, how to market that stuff, how to avoid internecine warfare and fanboy pointlessness. It also has demonstrated how to build a business where you can make real money.

So here are my observations: Mac OS X, and Apple's development paradigm, is the anti-Linux. And it's Steve Jobs' big accomplishment that Apple has built a better (I should actually say "more successful") Linux than Linus Torvalds has ever been able to do.