It's an editor, or an OS, or
Cmacs is a tabbed text editor which can be scripted using the Ccc programming language. It's under heavy development and currently has little practical value as a productivity tool.
The current release is meant to act as an anchor for developers interested in the Ccc language and/or experimentation with the Chrome platform.
Ccc is a Scheme derivative which covers most of the R5 spec while taking some liberties with omissions and extensions.
Cmacs includes a built-in Ccc API for editor manipulation. See the screenshot for an example.