GNU Zile is a text editor development kit, so that you can (relatively) quickly develop your own ideal text editor without reinventing the wheel for many of the common algorithms and data-structures needed to do so.
It comes with an example implementation of a lightweight Emacs clone, called Zemacs. Every Emacs user should feel at home with Zemacs. Zemacs is aimed at small footprint systems and quick editing sessions (it starts up and shuts down instantly).
Zile is a collection of algorithms and data-structures that currently support all basic Emacs-like editing features: it is 8-bit clean (though Unicode support is not ready yet), and the number of editing buffers and windows is only limited by available memoryand screen space respectively. Registers, minibuffer completion and auto fill are available.