http://github.com/davidswelt/aquamacs-emacs is the developers' repo, as stated at http://aquamacs.org/development.shtml .
Someone with permissions could add it to the ohloh's Enlistments (for Code Analysis).
The author has announced a now disfunctional site with the repository with the latest source in 2008 (see the announcement: http://comments.gmane.org/gmane.comp.window-managers.xwem.devel/926 ); that site is not running anymore -- http://archive.freesol.ru/arch/ . :(
So probably one should ask the author for the latest revision, or perhaps look into the source tree of SXEmacs ( http://sxemacs.org )...
(Another note: it's a pity XWEM doesn't work in GNU Emacs. I tried switching to XEmacs because of XWEM, but XEmacs felt quite a bit differently from the UI of GNU Emacs I'm accustomed to.)