Nils Weller's BSD-licensed C-compiler

http://nwcc.sourceforge.net/

Standalone converter for the OpenOffice.org writer and scalc formats

http://siag.nu/o3read/

Preferences manager for the Openbox window manager

http://openbox.org/wiki/Obconf

Securely delete file[s]

Menu manager for Openbox supporting both static and pipe menus

http://obmenu.sourceforge.net/

Objective Caml compiler and programming environment

https://ocaml.org/

Round clock application for X

OCR program implemented as filter

http://www.gnu.org/software/ocrad/ocrad.html

Help you update your snort rules after each update

http://oinkmaster.sourceforge.net/

Regular expressions library compatible with POSIX/GNU/Perl

https://github.com/kkos/oniguruma

A BSDL Regular Expressions library compatible with POSIX/GNU/Perl

http://www.geocities.jp/kosako3/oniguruma/

Oniguruma is a regular expressions library

http://www.geocities.jp/kosako3/oniguruma/

Open-source COBOL compiler

http://www.opencobol.org/

Motif X11 Toolkit (industry standard GUI (IEEE 1295))

https://motif.ics.com/

Open VMware tools for MidnightBSD VMware guests

https://github.com/vmware/open-vm-tools

Open VMware tools for FreeBSD VMware guests

https://github.com/vmware/open-vm-tools

3D positional spatialized sound library

http://www.openal.org/

Software implementation of the OpenAL specification

http://kcat.strangesoft.net/openal.html

Chemical toolbox designed to speak the many languages of chemical data

https://openbabel.org/wiki/Main_Page

Small, fast, standards compliant, extensible window manager

http://openbox.org/

Open Crypto Development Kit

http://www.gnutls.org/

OpenCORE implementation of AMR Narrowband & Wideband speech codec

http://sourceforge.net/projects/opencore-amr/

Middleware framework for smart card terminals

https://github.com/OpenSC/openct

Open Source Computer Vision library

https://www.opencv.org/

Open Source Computer Vision library

https://www.opencv.org/

Enterprise instant messaging server

https://www.igniterealtime.org/projects/openfire/index.jsp

Cisco implementation of H.264 codec

https://www.openh264.org/

Object-oriented SGML/XML parser toolkit and DSSSL engine

http://www.netfolder.com/DSSSL/

Oracle's Java 6 virtual machine release under the GPL v2

http://openjdk.java.net/

Oracle's Java 6 virtual machine release under the GPL v2

http://openjdk.java.net/

Java Development Kit 7

http://openjdk.java.net/

OpenJDK 7 FreeBSD binary

http://openjdk.java.net/

OpenJDK 8 FreeBSD binary

http://openjdk.java.net/

Open-source JPEG 2000 codec

https://www.openjpeg.org/

Open-source JPEG 2000 codec

https://www.openjpeg.org/

Open source LDAP client implementation

https://www.OpenLDAP.org/

Open source LDAP client implementation with SASL2 support

http://www.OpenLDAP.org/

Open source LDAP server implementation

https://www.OpenLDAP.org/

Libraries and utilities to access smart cards

https://github.com/OpenSC/OpenSC/wiki

Open-source implementation of the Service Location Protocol

http://www.openslp.org/

This package is a collection of SGML/XML tools called OpenSP

http://openjade.sourceforge.net/doc/

Graphical password applet for entering SSH passphrase

http://www.jmknoble.net/software/x11-ssh-askpass/

The portable version of OpenBSD's OpenSSH

https://www.openssh.com/portable.html

TLSv1.3 capable SSL and crypto library

https://www.openssl.org/

US tax prep software

http://opentaxsolver.sourceforge.net/

UPS daemon for some Belkin UPS's

http://frmb.org/openupsd.html

Secure IP/Ethernet tunnel daemon

https://openvpn.net/community/

IETF audio codec

https://opus-codec.org/

Oracle 8 client

http://www.grosbein.net/freebsd/oracle/

Calendar application for the Xfce Desktop

http://www.xfce.org/projects/orage/