https://bespin.mozillalabs.com/ –> http://ace.ajax.org/
https://mozillalabs.com/bespin/ –> http://ajaxorg.github.com/ace/build/editor.html
http://ftp.mozilla.org/pub/mozilla.org/labs/bespin/Embedded/BespinEmbedded-0.9a1.tar.gz
Also, good example of integration within CMS: http://edit.shiftcreate.com/overview