Here lie a bunch of open source projects, free for your perusal, and released under a liberal license that just asks for attribution, but is otherwise compatible with the MIT license (unless otherwise noted).
A versatile set of classes that allow you to quickly create many different kinds of setup assistant based user interfaces in Cocoa. Read about it, or grab it from github. For Mac OS X 10.4 (Tiger) or later.
TESharedObject improves upon the standard NSLock by allowing multiple readers to safely access shared data at the same time, and improves the quality of your multi-threaded code by enforcing good design principles. You can read about it or download it (github not setup yet). For Mac OS X 10.4 (Tiger) or later (may run on earlier systems too).
Dragonfly is a newLISP web framework I contributed a significant amount of code to (started by Marc Hildmann). It’s licensed under a different (but also liberal) license. You can read about it or get it from github.