http://rubyforge.org/project/showfiles.php?group_id=18&release_id=380
AEditor is a programmers editor for unix. It relies on Ncurses.
Its capable of: Folding, blocking, Macros, Undo/Redo...etc.
There is a huge testsuite (415 tests), so it should be stable.
However it lacks some things and consumes lots of memory.
Its written entirely in Ruby, so the code should be very easy
to grasp and extend, kind of Emacs with Ruby.