Open Source C User Interface (UI) Software for Mac

Code::Blocks is a free, open-source, cross-platform C, C++ and Fortran IDE built to meet the most demanding needs of its users. It is designed to be very extensible and fully configurable. Finally, an IDE with all the features you need, having a consistent look, feel and operation across platforms. Built around a plugin framework, Code::Blocks can be extended with plugins. Any kind of functionality can be added by installing/coding a plugin. For instance, compiling and debugging functionality is already provided by plugins! We hope you enjoy using Code::Blocks! The Code::Blocks Team

DragnDrop is a simple cross-platform utility to assist in debugging and monitoring drag-n-drop and clipboard interactions. It is of use to both developers and end users.

rngcc is "really nice GNU C compiler" it's the GUI for the standard GCC on Unix systems rngcc is fully written in c