Fangle is now ported to TeXmacs and bootstrapped within TeXmacs meaning that the fangle script is re-produced from fangle.tm by it's own operation.
So fangle is now developed in TeXmacs
TeXmacs is a great editor with expressive macro support allowing for full WYSIWYG literate programming experience.
An official release will be packed after the Savannah rename from newfangle to fangle, but for now, get it here:
http://git.savannah.gnu.org/cgit/newfangle.git/commit/?id=e228a76378171223346918baf626b6252e0649e9