Open Source Objective C To-Do Lists Software for Mac

Task Coach - Your friendly task manager. Task Coach is a free open source todo manager. It grew out of frustration about other programs not handling composite tasks well. In addition to flexible composite tasks, Task Coach has grown to include prerequisites, prioritizing, effort tracking, category tags, budgets, notes, and many other features. However, users are not forced to use all these features; Task Coach can be as simple or complex as you need it to be. Task Coach is available for Windows, Mac OS X, and GNU/Linux; and there is a companion iOS app.

GApp is for anyone that lives in GMail and/or uses GMail labels for Getting Things Done (GTD). GApp is focused on running the Google Apps on the Mac OS X desktop, allowing you to skin the GMail interface, and provides a searchable GTD view of your Inbox.

ToDoBee is a simple yet powerful task management application for Mac OS X. It is a user friendly and intuitive application that can be used for any IT related project as well as any general day to day task tracking/management situation.