Fizzilla, CHBrowserView, Cocoazilla, Camino
Let me give a little background, that might help. In the beginning, there was Mozilla. The widget and graphics layers were written with Quickdraw using all of the old Mac OS API calls. The app ran on OS8 and OS9. Then Apple released Mac OS X and they wanted a whole bunch of apps to run on it with limited tweaking. They munged all the old APIs into a reduced set called "Carbon". These are mostly legacy APIs, C-based. Many of them have existed since 1984. Also "introduced" with OS X was a totally separate UI toolkit called "Cocoa" based on the NeXTStep objective-C toolkit, cleaned up and repurposed for OS X, called "Cocoa". These toolkits live independently for the most part.