GNU libc's sysinfo port for FreeBSD

https://github.com/bsdimp/libsysinfo

ASN.1 structure parser library

https://www.gnu.org/software/libtasn1/

Flexible Communications Framework

http://telepathy.freedesktop.org/

Language guessing by N-Gram-Based Text Categorization

https://software.wise-guys.nl/libtextcat/

Text styling library

https://www.gnu.org/software/gettext/libtextstyle/manual/

Thai language support library

https://linux.thai.net/projects/libthai/

Theora video codec for the Ogg multimedia streaming system

https://www.theora.org/

Generic shared library support script

https://www.gnu.org/software/libtool/

BitTorrent Library

https://github.com/rakshasa/libtorrent

Lightweight fully POSIX compliant regexp matching library

https://laurikari.net/tre/

Integer-only fully Ogg Vorbis compliant decoder library

https://xiph.org/vorbis/

User space caching library

http://mercurial.creo.hu/repos/libublio

libudev-compatible interface for devd

https://github.com/wulf7/libudev-devd

Library for manipulating Unicode characters and strings

https://www.gnome.org/

Library of Unicode annotation data

http://libuninameslist.sourceforge.net/

Library for converting Unicode strings to numbers

http://billposer.org/Software/libuninum.html

Unicode string library

https://www.gnu.org/software/libunistring/

Library to work with RAR archivies

http://www.rarsoft.com/

Generic stack unwinding library

https://www.nongnu.org/libunwind/

Userspace read-copy-update (RCU) data synchronization library

http://lttng.org/urcu

Communication interface library for usbmuxd

http://www.libimobiledevice.org

The uTorrent Transport Protocol library and sample utilities

https://github.com/bittorrent/libutp

Multi-platform support library with a focus on asynchronous I/O

https://github.com/libuv/libuv

Video4Linux library

https://linuxtv.org/wiki/index.php/V4l-utils

VAAPI wrapper and dummy driver

https://github.com/intel/libva

VAAPI wrapper for GLX

https://github.com/intel/libva

VDPAU wrapper and tracing library

http://freedesktop.org/wiki/Software/VDPAU

Abstraction library that sits between apps and visual plugin

http://libvisual.sourceforge.net/

Provide an easy API to a custom vnc server

http://libvnc.github.io/

Library to provide file system type information

Audio compression codec library

https://xiph.org/vorbis/

VP8/VP9 reference encoder/decoder

https://www.webmproject.org/

Adds tablet support to libinput

https://github.com/linuxwacom/libwacom/wiki

Tools and library for converting Microsoft WMF (windows metafile)

http://wvware.sourceforge.net/libwmf.html

Tools and library for converting Microsoft WMF (windows metafile)

http://wvware.sourceforge.net/libwmf.html

Library used for writing pagers and taskslists

https://www.gnome.org/

Library used for writing pagers and taskslists

http://www.gnome.org/

Tools for importing and exporting WordPerfect(tm) documents

http://libwpd.sourceforge.net/

Window Maker raster graphics library

http://www.windowmaker.org/

The W3C Reference Library

http://www.w3.org/Library/

Library for encoding H.264/MPEG-4 AVC video

http://www.videolan.org/x264.html

Mesa XA state tracker

https://www.mesa3d.org/

The X protocol C-language Binding (XCB) library

https://xcb.freedesktop.org/

Implementation of the XDG Base Directory specification

https://github.com/devnev/libxdg-basedir/

Various Gtk widgets for the Xfce Desktop

http://www.xfce.org/

Widgets library for the Xfce desktop environment

https://www.xfce.org/

Extension library for the Xfce desktop environment

https://www.xfce.org/

Libraries for xine multimedia player

http://www.xine-project.org/

Keymap handling library for toolkits and window systems

https://xkbcommon.org/

XKB file library

https://www.freedesktop.org/Software/xorg