The newest version code from CVS is fine with Emacs 23.X. You can install it from CVS like below.
$ cvs -d :pserver:anonymous@cvs.namazu.org:/storage/cvsroot login
$ cvs -d :pserver:anonymous@cvs.namazu.org:/storage/cvsroot co emacs-w3m
$ cd emacs-w3m
$ w3m -version # check version
$ autoconf
$ ./configure --help # check options
$ mkdir ~/Dropbox/emacs/.emacs.23.2.d/lisp/emacs-w3m
$ ./configure --with-emacs=/Applications/Emacs-23.2/Emacs.app/Contents/MacOS/Emacs \
--with-lispdir=/Users/aka/Dropbox/emacs/.emacs.23.2.d/lisp/emacs-w3m \
--infodir=/Users/aka/Dropbox/emacs/.emacs.23.2.d/info/
$ make
$ make install