Here is the Apple statements on Open Source and how it contributes back to the Open Source community.
As the first major computer company to make Open Source development a key part of its ongoing software strategy, Apple remains committed to the Open Source development model. Major components of Mac OS X, including the UNIX-based core, are made available under Apple’s Open Source license[This is the Darwin component core of the overall MacOS/X], allowing developers and students to view source code, learn from it and submit suggestions and modifications. In addition, Apple uses software created by the Open Source community, such as the HTML rendering engine for Safari, and returns its enhancements to the community.
Apple believes that using Open Source methodology makes Mac OS X a more robust, secure operating system, as its core components have been subjected to the crucible of peer review for decades. Any problems found with this software can be immediately identified and fixed by Apple and the Open Source community.
If you’re a developer, we invite you to inspect Mac OS X under the hood, free of charge, by joining the Darwin development process or just see a sampling of the Open Source projects used and created by Apple
Open Source Projects:
Project Version Where
CDSA-Common Data Security Arch. 279 Apple
Darwin 8 Apple
HeaderDoc doc generator 8.5.9 Apple
OpenDirectory 10.4 Apple
QuickTime Streaming Server 489 Apple
BonJour 107 Apple
WebCore 2 Apple
X11.app 0.4 Apple
Now what is interesting is that the list of Open Source projects that Apple uses is broader and deeper by probably an order of magnitude to what it has contributed back to the open source community.