This project is Aquamacs Emacs, a modified distribution of Emacs for Mac OS X.
Aquamacs tracks GNU Emacs, merging from the latest release branch. Aquamacs is not a fork.
Aquamacs is designed to make it easy for users to get started with Emacs. It also makes it easy to switch between different programs on the Mac. Further, Aquamacs comes with many packages pre-installed and configured so that users can, for example, start editing LaTeX documents with AUCTeX or statistical programs in R using ESS-Mode. Many programming languages are supported, and sometimes Aquamacs provides, by default, other major modes for certain programming languages than what comes with GNU Emacs.
Development on Aquamacs contributes back to GNU Emacs where appropriate.
Aquamacs Emacs is licensed under the GNU General Public License, v3.
Project website: http://aquamacs.org
Call ./build-aquamacs, or "make bootstrap; make install".
Please contact the aquamacs-devel mailing list. (Developers only; Users should obtain support via the Emacs on OSX mailing list.)
Aquamacs Emacs started in 2005. Since then, it has been maintained by David Reitter, david.reitter@gmail.com. Many developers have since contributed to its success.