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 and iPhoto), and devices (e.g., Apple TV and AirPort). Developers can easily leverage Bonjour from both OS X and iOS.
OS X offers a standard Java environment for running Java Applets through the Safari browser or for development with the complete Java Development Kit (JDK). The JDK is automatically downloaded and installed as soon as you try to run any software that depends upon Java. With support from popular open source IDEs such as Eclipse or NetBeans, the Mac is a great platform for running and developing Java applications.
The most widely-sold UNIX operating system, OS X combines a fully-conformant UNIX foundation with the richness and usability of the Macintosh interface. View Developer Documentation
WebKit is the open source web browser engine at the heart of Apple's Safari web browser on Mac, Windows, and iOS. It also provides a system-level framework engine that powers Dashboard, Mail, and many other OS X apps.
Apple Opensource Approach
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 core, are made available under Apple’s Open Source license, 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.