Similar to PostgreSQL

Leafpad

Libavcodec

Libjpeg

Libpng

LibreSSL

Librsvg

Libvirt

Libwww

Lighttpd

Linux-libre

Linux kernel

LIRC

Lis (linear algebra library)

Mesa (computer graphics)

Metacity

TinySPARQL

MicroEMACS

MicroPython

MiKTeX

Mined (text editor)

Mintty

Mirai (malware)

MLDonkey

MPICH

MsQuic

MuPDF

Musl

Mutter (software)