Hemlock is another Emacs implemented in Common Lisp. I don't know how it differs from Climacs except the latter obviously uses CLIM as its front end. Modified versions of Hemlock are used as the IDE editors for CCL and Lispworks.
Yes but...LispWorks doesn't include [most of] the source of their editor, so I cannot modify or customize it much. CCL includes the entire source, which means one can customize it as much as one wishes.
https://en.wikipedia.org/wiki/Hemlock_(text_editor)