It's more open than you would think; They incorporate 200+ open source projects in to the OS and that's code that they return to the community. (Webkit is a good example.)

http://www.apple.com/opensource/

Darwin, Grand Central Dispatch are some other examples that I can think of.

Apple had a brief moment where they were swept up in the excitement of the Open Source revolution, and it was a contributing factor to their revival amongst hackers.

They've since regained their senses, and now only choose open when it's the only way for them to compete effectively (for example, if they are facing off against a seemingly unbeatably strong foe, like Microsoft or Adobe, they will opt for openness because it tilts the playing field, but if they have a near-monopoly they will be the most tightly controlled vendor in the space...such as in smart phones).

Openness for Apple is not an end, it is a means to an end. Money and market strength are the goals, even if it is at the expense of consumers and developers.

In short, this article is from 2005, though I think many folks are still under the misapprehension that Apple products are "open", when they are actually often even worse than Microsoft products in terms of openness, which is pretty darned bad (though it's also a reflection of the fact that Microsoft has become more open in the intervening years due to market pressure and a few gadflies within Microsoft).

He's talking about a powerbook. By open, he means what happens when you lift the screen.