Last week I was listening to episode 203 the MacBreak Weekly Podcast. I agree with most everything that's talked about on the episodes I've listened to and for the most part this one was much the same, except for the one member of the panel insisting that Apple should open source OS X. Let me be one to say that there is absolutely no way that OS X will ever be open sourced. There are so many reasons that this will never happen it's ridiculous. Here's a few off the top of my head:
Traditional computing devices aren't dead yet
The notebook is far from dead. The desktop maybe, but not the notebook. iOS isn't feature rich enough to replace a traditional computer for the vast majority of people. There are lots of places where the OS shines, but for general purpose computing it's not there yet. You can tell that this sentiment is echoed by Apple in the fact that iDevices are treated as satellites that have to sync up with the mothership Mac.
OS X is required for iOS development, why lose out on a sale?
Right now the only platform that you can develop iOS applications on is OS X. The only hardware that you can (legally) run OS X on is a Mac. Apple makes a sizeable amount of revenue off of Mac sales. If they were to open source the platform they'd been losing Mac sales. Why would they want to cut off that revenue stream?
OS X is encumbered
Probably the main reason that Apple will not open source OS X is that it legally can't. Unlike full open source operating systems like Linux, OS X probably contains lots of code that's been licensed from third parties. What code might that be? It could be anything. For an example of this, have a look at OS/2.
Unlike OS X, OS/2 was actually discontinued. Some years later devoted users and businesses that had bought into the operating system wanted it to be open sourced. IBM refused citing licensing problems over some of the code that makes up the OS. This is coming from a company that does a lot of open source work. If they could, I'm sure they would open source it but legally they can't. It's not worth their time or the potential for law suits.
Apple is not going to open source OS X.