Macworld UK have posted this (IMO rather sensationalist) article saying that Apple has closed down OS X, ie the source code is no longer available. In fact what they’ve done (and I believe they announced this months ago, so it’s hardly news) is closed the x86 kernel and drivers. All the other parts of Darwin that were open source, still are. I think Macworld’s just trying to stir things up and grab some extra page views here.
The main reason for closing the source is, allegedly, that Apple want to make it harder for people to hack the OS to run well on PCs. (I’m sure they’ll find a way though, whether the kernel is closed or open.)
Frankly it doesn’t bother me much that the kernel isn’t open source, as long as it works and I can get my work done! It’s not like Mac OS is a Free Software operating system in the first place. And personally I’ve never had to hack the Linux kernel to suit my needs, so I doubt I’d be wanting to hack the Mac OS one either. I’m a bit concerned that the lack of peer review might lead to a less stable and less secure kernel, but we’ll see.
As for the article’s argument that research scientists won’t be able to compile a custom kernel – well there’s always Linux or FreeBSD isn’t there!