The Omni Group has made available some of the source code written for their Mac OS X and iPhone applications.
The code available for use under the terms specified in the Omni Source License (basically the MIT license). They have not yet provided any formal documentation, though the source code does include a limited amount of internal documentation.
These frameworks include the following (in their own words):
- OmniBase is the lowest level framework in the Omni framework suite, used by every product we ship. OmniBase provides a series of debugging aids for class allocation and initialization, an alternative assertions mechanism, several Objective-C runtime manipulation aids, and a very reliable, cross-platform implementation of +load (called +didLoad).
- OmniFoundation is our extension to Apple's Foundation framework. Besides several extremely useful extensions to Apple Foundation classes, OmniFoundation provides a horde of unique and powerful classes. OmniFoundation is a veritable treasure chest of programming goodies. Take a look for yourself.
- OmniAppKit is our set of extensions to Apple's AppKit.framework, full of cool stuff to make Mac OS X application development even easier. Some highlights include OAOSAScript, OAPreference, and OAFindPanel. OmniAppKit also includes lots of extensions to Apple's classes to make creating rich user interfaces much easier.
- OmniDataObjects provides a CoreData-like API, but with a much smaller feature set (and thus implementation). Built on top of SQLite, OmniDataObjects provides the persistence for OmniFocus on the Mac and iPhone.
- OmniInspector, the inspector framework as seen in OmniGraffle, OmniFocus, OmniOutliner and OmniPlan!
- OmniNetworking provides a simple and extensible Objective-C wrapper to a multitude of complex networking constructs. Communication over several internet standard protocols is supported, including TCP, UDP and Multicast. Writing a simple FTP client, or custom TCP/IP-based server program becomes a trivial task using OmniNetworking.
You can download the latest version of the frameworks, which currently require Mac OS X 10.5 "Leopard" and Xcode 3.0 or later.