OpenTBS - Skrol 29
OpenTBS is an open source plugin for the TinyButStrong template engine, allowing users to easily create OpenOffice and MS Office documents.

Orta Cinnamon Light
Orta Cinnamon Light is an open source theme for the Cinnamon desktop environment, a port of the Orta GNOME Shell created by Half-Left.

OSX Like
OSX Like is a free theme for the Cinnamon desktop environment that makes it look just like the Mac OS X desktop. It contains:

Onion Tou Cairo Clock
Onion Tou Cairo Clock is an open source skin for the Cairo-Clock screenlet inspired by the manga character Onion Tou.

Osirion
Osirion is a free Cinnamon theme, specially designed to work with Cinnamon 1.6 or later. The wallpaper from the screenshot is included in the archive.

Ostfriesland
Ostfriesland is an open source GNOME-Shell theme specially designed for the GNOME 3.6.x desktop environment. It is based on the Frieze theme created by Jacob van ...

OldWoodAndSteel
OldWoodAndSteel is an open source GTK2 theme especially designed for the MATE desktop environment. It provides a wood and steel look and feel and includes the ...

October
October is an open source, dark, thin, minimalistic, but usable Metacity window decoration. It is designed to be used with the Sans Bold 7 Window ...

OSX-Nostalgie
OSX-Nostalgie is an open source icon theme specially designed for users of the GNOME desktop environment who want an Apple Mac OS X look-a-like icon set.

Ocean Clock
Ocean Clock is an open source theme for Cairo-Clock that uses pete333's hour, minute and second hands.

OfficeFloor - Officefloor
OfficeFloor is an open source software that empowered web developers to easily build real-time Web apps that are cross-platform.

OhM-shell
OhM-shell is an open source alternative to the GNOME-Shell user interface of the GNOME 3 desktop environment, written in Python and GTK3.

OS
OS is an open source theme for the GNOME Shell interface, that tries to mimic launchpad interface of the Apple Mac OS X operating system.

Optimus Blue Inspiration
Optimus Blue Inspiration is a blue theme with a dark glossy transparent style, specially designed for GNOME's user interface, GNOME-Shell.

Oxygen Orange
Oxygen Orange is a Metacity window decoration based on the original Oxygen style, but modified to match the Human color scheme in the Ubuntu operating ...

Orange-arch for Metacity
Orange-arch is an orange Metacity window decoration based on the Orange-arch GTK2 theme created by Josip Ponjavić.

OSS4 Mixer
OSS4 Mixer is a GNOME Shell extension that provides a volume controller for the OSS4 sound system output (vmix0-outvol or other).

Oxygen-4.1
Oxygen-4.1 is a Metacity window decoration for the GNOME desktop environment, a port of the Oxygen theme.

Old Steampunk 3.4
Old Steampunk 3.4 is a re-implementation of the old Steampunk theme for the GNOME Shell user interface of the GNOME desktop environment.

OMG_Suite
OMG_Suite is a dark GTK3 and GTK2 theme for the GNOME desktop environment.

Old Network Managger
Old Network Managger is a GNOME Shell extension that will implement a "Connection Editor" entry in the network menu, allowing users to access the old-style ...

Overlay Followfocus
Overlay Followfocus is a GNOME Shell extension that will modify the GNOME overview mode in such a way that allows for fast switching between opened apps.

ODK Briefcase - OpenDataKit
ODK Briefcase is an open source software that enables developers to easily connect to an ODK Aggregate server in order to retrieve the data and ...

ODK Aggregate - OpenDataKit
ODK Aggregate is an open source application, written in Java, that provides a ready-to-deploy data and server repository.