Free and Open Source Software, also F/OSS or FOSS, is software which is liberally licensed to grant the right of users to study, change, and improve its design through the availability of its source code. F/OSS is generally synonymous with free software and open source software, and describes the same licenses, culture, and development models.
Some examples of FOSS software include: the Linux kernel, GNOME Desktop, and FreeBSD.
The most well known and popular F/OSS licenses include: GNU General Public License (GPL), GNU Lesser General Public License (LGPL), BSD license, Apache License, MIT License and Mozilla Public License.
There are a number of endorsed F/OSS definitions, and related lists of licenses. The above licenses are approved by all definitions.
F/OSS definitions and guidelines:
Open Source Definition, from the Open Source Initiative
Free software definition, from the Free Software Foundation
Debian Free Software Guidelines
Lists of licenses:
OSI approved licenses
The Free Software Foundation's list of free and unfree licenses
The phrase Free/Libre/Open-Source Software, or FLOSS, (see also the similarly derived FOSS) is an inclusive term designed to be neutral when referring to both free software and open source software.
Often both free software and open software can refer to the same program or source code, but each term represents a differing emphasis on the importance of freedom (free software) or technical progress (open source software).
The term FLOSS is often used to bridge the ideological divide between the free software and open source software movements. The term FLOSS is useful for those who, for a variety of reasons, do not want to align themselves with one group and alienate the other. FLOSS can also be used as a neutral term when discussing free / open source software with those of differing ideological viewpoints.
Historically, FLOSS was first used as a project acronym by Rishab Aiyer Ghosh. In 2001 the European Commission (EC) used the phrase when they funded a study on the topic, and in July 2002 they further popularised the acronym by publishing both a FLOSS survey and study and a FLOSS workshop report. The EC chose FLOSS as an inclusive acronym that hopefully would not further antagonize the main participants in the naming controversy. Although neither side has shown much enthusiasm for FLOSS or any other all inclusive phrase, Richard Stallman has acknowledged and recommended use of the phrase Free/Libre/Open Source Software by those who refuse to commit themselves explicity to his philosophical approach.
In constructing the FLOSS phrase, the French/Spanish word libre was included to emphasize the "freedom from entanglements" meaning of the English word free, as opposed to the unintended (but frequently assumed) "pay no money" meaning. The similarly derived acronym FOSS avoids using libre not because of any disagreement with this clarification, but to avoid collision with the English word "floss".