Belcard is a C++ library to manipulate the vCard standard format files.

belle-sip is a SIP (RFC3261) implementation written in C, with an object oriented API.

Belr parses input formatted according to a language defined by an ABNF grammar, such as the protocols standardised at IETF.

bzrtp is a FOSS implementation of ZRTP keys exchange protocol.
The library written in C 89, is fully portable, and can be executed
on many platforms including x86 and ARM processors.

LIME is an encryption library for one-to-one and group instant messaging, allowing users to exchange messages privately and asynchronously. It supports multiple devices per user and multiple users per device.

LIME offers two major security benefits to instant messaging users:
* End-to-end encryption, which means that only you and your contact (and not even the server) can decrypt the content that you shared.
* Perfect forward secrecy, which ensures that encrypted messages cannot be decrypted by a third party, even if a key is compromised in the future.

Linphone is a Web phone with a Qt interface.
It lets you make two-party calls over IP networks such as the Internet.
It uses the IETF protocols SIP (Session Initiation Protocol) and RTP (Real-time Transport Protocol) to make calls, so it should be able to communicate with other SIP-based Web phones. With several codecs available, it can be used with high speed connections as well as 28k modems.

Linphone is a Web phone with a Qt interface.
It lets you make two-party calls over IP networks such as the Internet.
It uses the IETF protocols SIP (Session Initiation Protocol) and RTP (Real-time Transport Protocol) to make calls, so it should be able to communicate with other SIP-based Web phones. With several codecs available, it can be used with high speed connections as well as 28k modems.

mediastreamer2 is a GPL licensed library to make audio and video real-time streaming and processing.
Written in pure C, it is based upon the oRTP library.

oRTP is a LGPL licensed C library implementing the RTP protocol (rfc1889).

MuPDF is a lightweight PDF and XPS viewer and parser/rendering library.

The renderer in MuPDF is tailored for high quality anti-aliased graphics. It renders text with metrics and spacing accurate to within fractions of a pixel for the highest fidelity in reproducing the look of a printed page on screen.
MuPDF is also small, fast, and yet complete. It supports PDF 1.7 with transparency, encryption, hyperlinks, annotations, search and many other bells and whistles. MuPDF can also read XPS documents (OpenXPS/ECMA-388).

The paper package enables users to indicate their preferred paper
size, provides the paper(1) utility to find the user's preferred
default paper size and give information about known sizes, and
specifies system-wide and per-user paper size catalogues, which can be
can also be used directly (see paperspecs(5)).

Paper is based on libpaper: see AUTHORS for more information.

The Shoreline Firewall, more commonly known as Shorewall, is a Netfilter (iptables) based firewall that can be used on a dedicated firewall system, a multi-function gateway/router/server or on a standalone GNU/Linux system

Remmina is a remote desktop client written in GTK+, aiming to be useful for system administrators and travellers, who need to work with lots of remote computers in front of either large monitors or tiny netbooks. Remmina supports multiple network protocols in an integrated and consistent user interface. Currently RDP, VNC, SPICE, NX, XDMCP, SSH and EXEC are supported.

A window manager for the X Window System that can emulate the look of
Windows '95, OS/2 Warp 3, OS/2 Warp 4, and Motif and tries to take the
best features from those systems. IceWM features multiple workspaces,
opaque move and resize, a taskbar, a window list, mailbox status, and a
digital clock. It is fast and small.