Complete rewrite of the NASM assembler

https://yasm.tortall.net/

General-purpose console screen reader

http://yasr.sourceforge.net/

Yet Another LaTeX mode and html mode on Emacs

http://www.yatex.org/

Z39.50/SR client and API library

https://www.indexdata.com/resources/software/yaz/

Diff readability enhancher for color terminals

https://github.com/ymattw/ydiff

Terminal wrapper for creating drop-down consoles

http://phrat.de/yeahtools.html

Minimal X11 window manager with BeOS-like tabbed titles

http://phrat.de/

Help browser for the GNOME 3 desktop

https://www.gnome.org/

Utilities to help manage documentation for Yelp and the web

https://wiki.gnome.org/Apps/Yelp/Tools

DocBook XSLT stylesheets for yelp

https://www.gnome.org/

Free (GPL) encoder and decoder for the yEnc Usenet file format

http://www.yencode.org/

Amateur Radio curses based logging program

https://fkurz.net/ham/yfklog.html

Yubico C client library

https://developers.yubico.com/yubico-c-client/

Library and tool for personalization of Yubico's YubiKey

https://developers.yubico.com/yubikey-personalization/

Command-line YAML and XML processor, jq wrapper for YAML/XML documents

https://github.com/kislyuk/yq

Unpack data in MS Outlook TNEF format

https://github.com/Yeraze/ytnef

Yubico PIV tool

https://developers.yubico.com/yubico-piv-tool/

Seamless ssh-agent for YubiKeys

https://filippo.io/yubikey-agent

The Yahoo! JavaScript and CSS Compressor

https://yui.github.io/yuicompressor/

Tool to decode yEnc encoded files

http://yydecode.sf.net/

Dynamically typed N-D expression system based on xtensor

https://github.com/xtensor-stack/zarray

Puzzle game where the player has to arrange balls in triplets

https://zaz.sourceforge.net/

ZBar barcode reader

http://zbar.sourceforge.net

Compressed file format that splits the file into independent chunks

https://github.com/zchunk/zchunk

Encrypted, secure compressed TCP tunnel

http://www.winton.org.uk/zebedee/

Free RIPv1, RIPv2, OSPFv2, BGP4 route software (server/reflector)

http://www.zebra.org/

Z39.50/SR server software

http://www.indexdata.dk/zebra/

Event logging framework

https://wiki.gnome.org/Projects/Zeitgeist

Framework for developing PHP web applications

https://framework.zend.com/

Display GNOME dialogs from the command line

Simpler web photo gallery

https://www.zenphoto.org/

Network virtualization everywhere

https://www.zerotier.com/

Zetaback ZFS backup and recovery management system

https://github.com/omniti-labs/zetaback/

Simple way of maintaining zfs snapshots using the periodic system

http://www.neces.com/blog/technology/integrating-freebsd-zfs-and-periodic-snapshots-and-scrubs

ZFS Snapshot Replication Script

https://github.com/leprechau/zfs-replicate

Tool to sieve ZFS snapshots as per given spec a la 'pdumpfs-clean'

https://github.com/knu/zfs-snapshot-clean

Automatic ZFS snapshot management tool

http://marcin.studio4plus.com/en/zfs-file-history/howto.html

Display human-readable ZFS statistics

http://www.vx.sk/zfs-stats/

Simple sh script to make zfs rolling snaphosts with cron

https://github.com/graudeejs/zfSnap/

OpenSolaris-compatible auto snapshotting for ZFS

https://github.com/bdrewery/zfstools

Zoner's Half-Life compile tools

http://zhlt.info/

Small emacs-like text editor

http://www.gnu.org/software/zile/

Distributed computing project

http://zillion.sourceforge.net/

Create/update ZIP files compatible with PKZIP

http://infozip.sourceforge.net/Zip.html

Produce .ZIP file from two other ones with the best compressed files

http://www.advsys.net/ken/utils.htm

Tool for inspecting the contents of a compressed archive

http://xanthippe.dyndns.org/Zipper/

Tool to manage keys and signatures for DNSSEC-zones

https://www.hznet.de/dns/zkt/

Fork of the zlib data compression library

https://github.com/zlib-ng/zlib-ng

Internet scanner

https://zmap.io/

ZnapZend is a ZFS centric backup tool

https://www.znapzend.org/