[Star Traveler]

OPEN SOURCE

Apple was the first major computer company to make Open Source development a key part of its software strategy, and continues to both use and release significant quantities of open source software.

Bonjour

Bonjour, also known as zero-configuration networking, enables automatic discovery of computers, devices, and services on IP networks using industry standard IP protocols. It is a key component of Apple applications (e.g., iTunes, iPhoto), services (e.g., MobileMe) and devices (e.g., Apple TV, and Airport). Developers can easily leverage Bonjour from both Mac OS X and iPhone OS.
View Reference Documentation

Source Code

Bonjour is not only based on open Internet standards, our implementation is available as Open Source under the Apache 2.0 license. It is built into most modern printers and many other consumer products.

• Bonjour Source Code
• Bonjour Conformance Test
• Bonjour Printing Specification (PDF)

Windows

Bonjour is also available for Windows, both as an end-user tool for printer discovery and an SDK allowing developers to distribute Bonjour as part of their application.

• Bonjour SDK for Windows
• Bonjour Print Services for Windows
• Licensing and Trademarks

Java

Mac OS X comes complete with a fully configured and ready-to-use standard Java environment for running Java Applets through the Safari browser, or for development with the complete Java Development Kit (JDK). Nothing to download, it all just works when you crack the lid of a new Mac, and Java is regularly updated as part of Apple’s Software Update. With support from popular open source IDEs such as Eclipse or NetBeans, the Mac is a great platform for running and developing Java applications.
View Reference Documentation

Unix

The most widely-sold UNIX operating system, Mac OS X combines a fully-conformant UNIX foundation with the richness and usability of the Macintosh interface. View
Reference Documentation

WebKit

WebKit is the open source web browser engine at the heart of Apple's Safari web browser on Mac, Windows, and iPhone OS. It also provides a system-level framework engine that powers Dashboard, Mail, and many other Mac OS X applications.

• View Reference Documentation
• Safari Dev Center
• Webkit Open Source Project

[OneWingedShark]

Haven't we had this discussion?
As I recall I made the point that unix is a horrible OS because it shares the same [mis-]design principals as C & C++. [It is impossible to separate the two, as intertwined as they are.] While it is, IMO, good to have as much of the OS in as high a level language as early as possible; C & C++ are a step backwards for Apple (they used to make their interfaces in Pascal).

As it stands, I'm of the opinion that Ada is an excellent choice for OS development, the language itself has constructs that map DIRECTLY to the some of the challenges that are being addressed right now, notably concurrency/multi-proccessors.

Unix Hater's Handbook