These binaries were all built from SeaMonkey's 2.53 GitLab repositories, off
the 2_53_20_final branch, and Mozilla's repositories for the extensions, off the
default branch, with the following commands used to obtain the sources:

   git clone -b 2_53_20_final https://gitlab.com/seamonkey-project/seamonkey-2.53-mozilla.git comm-253
   cd comm-253
   git clone -b 2_53_20_final https://gitlab.com/seamonkey-project/seamonkey-2.53-comm.git comm 

A source code tarball with the contents of all the repositories, ready to
build, is available for download from the source/ subdirectory here on FTP.

For the l10n source, these are from SeaMonkey's 2.53 GitLab repositories, off
the 2_53_20_final branch, with the following commands used to obtain the source:

   git clone -b 2_53_20_final https://gitlab.com/seamonkey-project/seamonkey-2.53-l10n.git l10n-253

A source l10n tarball with the contents of l10n-253 in such a checkout is
available for download from the source/ subdirectory here on FTP.

This directory contains precompiled binaries of SeaMonkey 2.53.20

Read https://www.seamonkey-project.org/dev/ for instructions on how to build
your own copy of SeaMonkey.

Language packs are available from the langpacks/ subdirectory and can be
installed as add-ons and switched to using the Appearance preferences.

linux-i686 and linux-x86_64 .tar.bz2 files are tarball builds for Linux on the
x86 and x86_64 platforms.

mac/ .dmg files are self-mounting disk images for macOS.

The .exe files in win32/ and win64/ are the main win32/win64 release installers
respectively, letting you chose which extensions to install.

The .zip files in win32/ and win64/ contain a full optimized build without an
installer. Accessibility and MAPI OS integration are not available if you use a
zipped Windows build. If you do not understand how to get this to run, you
should use installer.exe instead.

Please read the release notes at
  https://www.seamonkey-project.org/releases/seamonkey2.53.20/