How to from source?

You will need Xcode tools to perform this operation.

MacBook-Pro: mkdir src
MacBook-Pro: cd src
MacBook-Pro: cvs -z3 -d:pserver:anonymous@cvs.sv.gnu.org:/sources/emacs co emacs
MacBook-Pro: cd emacs
MacBook-Pro: ./configure --with-ns --with-jpeg=no --with-gif=no --with-tiff=no
MacBook-Pro: make bootstrap
MacBook-Pro: make
MacBook-Pro: make install
MacBook-Pro: sudo cp -r nextstep/Emacs.app /Applications/Emacs.app

if you would like to use it in terminal

MacBook-Pro: cd src
MacBook-Pro: make
MacBook-Pro: cp emacs /usr/bin/emacs
MacBook-Pro: emacs --version
GNU Emacs 23.1.90.1
Copyright (C) 2009 Free Software Foundation, Inc.
GNU Emacs comes with ABSOLUTELY NO WARRANTY.
You may redistribute copies of Emacs
under the terms of the GNU General Public License.
For more information about these matters, see the file named COPYING
MacBook-Pro: emacs -nw