Library for multilingual text handling

http://www.nongnu.org/m17n/

GNU M4

https://www.gnu.org/software/m4/m4.html

Bonjour (zero-configuration networking) by Apple

https://developer.apple.com/bonjour/

Apple mDNS responder - BSD nsswitch module

https://developer.apple.com/bonjour/

Madplay MP3 player (part of MAD project)

https://www.underbit.com/products/mad/

Magus runtime utilities for build cluster

Utilities, daemons, and filters for processing e-mail

https://mailutils.org/

Dependency generator for makefiles

https://www.x.org/archive/X11R7.5/doc/man/man1/makedepend.1.html

Perl scripts to assist in the generation and application of patches

https://www.vromans.org/johan/software/sw_makepatch.html

Convert man pages to HTML

http://man2web.sourceforge.net/

UNIX manual page editor and viewer

http://freecode.com/projects/manedit

Multithreaded SQL database (client)

http://mariadb.org/

Multithreaded SQL database (server)

http://mariadb.org/

Allows Maven's artifact handling to be used from within an Ant build

http://maven.apache.org/ant-tasks/index.html

Wrapper script for the various installations of Maven

Java project management tool, 2.0 branch

http://maven.apache.org/maven2/index.html

Java project management tool, 3.x branch

http://maven.apache.org/

Implementation of new/posix awk

http://invisible-island.net/mawk

Converts mbox mailboxes to Maildir

http://batleth.sapienti-sat.org/projects/mb2md/

Motherboard monitor for LM78/79, W8378x, AS99127F, VT82C686 and ADM9240

http://www.nt.phys.kyushu-u.ac.jp/shimizu/download/download.html

Midnight Commander, a free Norton Commander Clone

http://www.midnight-commander.org/

Lightweight Midnight Commander clone

http://mc.linuxinside.com/

Collects and decodes Machine Check Exception data

http://mcelog.org/

Replacement for crypt(1)

http://mcrypt.sourceforge.net/

Utilities and libraries to export data from MS Access databases (.mdb)

http://mdbtools.sourceforge.net/

Alcohol 120% to ISO converter

https://BSDforge.com/projects/sysutils/mdf2iso/

Advertise a service via Rendezvous

https://github.com/Pro/mdnsd/

Open Source implementation of the Lotus Sametime protocol

http://meanwhile.sourceforge.net/

Wiki engine used by Wikipedia

http://www.mediawiki.org/

GNOME visual diff and merge tool

http://meldmerge.org/

High-performance distributed memory object cache system

https://memcached.org/

Utility to test for faulty memory subsystem

http://pyropus.ca/software/memtester/

Menu generator for X Window Managers and desktop environments

http://menumaker.sourceforge.net/

Fast, lightweight source control management system

https://www.mercurial-scm.org/

OpenGL demos distributed with Mesa

https://www.mesa3d.org/

OpenGL hardware acceleration drivers for DRI2+

https://www.mesa3d.org/

OpenGL libraries that support GLX and EGL clients

https://www.mesa3d.org/

High performance build system

https://mesonbuild.com/

Window manager for the adult in you

Metalink generation tool

http://metalinks.sourceforge.net/

Implementation of MIME, the Multipurpose Internet Mail Extensions

Package for unstructured graph partitioning

http://glaros.dtc.umn.edu/gkhome/metis/metis/overview

Small, fast Emacs-like editor

https://github.com/ibara/mg

Easy-to-use library for strong hashes such as MD5 and SHA1

http://mhash.sourceforge.net/

MidnightBSD desktop environment

http://people.midnightbsd.org/~laffer1

Lightweight web browser using WebKit browser engine

https://www.midori-browser.org/

Mod player which plays MTM, STM, XM, MOD, S3M, ULT, UNI and IT mods

http://mikmod.sourceforge.net/

Construct and optionally send MIME messages from command line

http://www.argon.org/~roderick/

MIME Media Types list

http://packages.qa.debian.org/m/mime-support.html

Infiniminer/Minecraft inspired game

http://minetest.net/