Free-and-Open-Source-Software (FOSS) is software that is liberally licensed to grant the right of users to study, change, and improve its design through the availability of its source code. In the context of free and open source software, "free" is intended to refer to the freedom to copy and re-use the software, rather than to the price of the software.

FOSS is an inclusive term which covers both free software and open source software which, despite describing similar development models, have differing cultures and philosophies. Free software focuses on the philosophical freedoms it gives to users while open source focuses on the perceived strengths of its peer-to-peer development model. FOSS is a term that can be used without particular bias towards either political approach.

Free software licences and open source licenses are used by many software packages. The licenses have important differences, which mirror the differences in the ways the two kinds of software can be used and distributed and reflect differences in the philosophy behind the two.

Free software is software that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with minimal restrictions only to ensure that further recipients can also do these things and that manufacturers of consumer-facing hardware allow user modifications to their hardware. Free software is generally available without charge, but can have a fee.

Open source license is a copyright license for computer software that makes the source code available under terms that allow for modification and redistribution without having to pay the original author. Such licenses may have additional restrictions such as a requirement to preserve the name of the authors and the copyright statement within the code. One popular (and sometimes considered normative) set of open source software licenses are those approved by the Open Source Initiative (OSI) based on their Open Source Definition (OSD).

A Brief History

The free software movement was conceived in 1983 by Richard Stallman to satisfy the need for and to give the benefit of "software freedom" to computer users. Stallman founded the Free Software Foundation (http://www.fsf.org) in 1985 to provide the organizational structure to advance his Free Software ideas.

From 1998 onward, alternative terms for free software came into use. The most common are "software libre", "free and open source software" ("FOSS") and "free, libre and open source software" ("FLOSS"). The antonym of free software is "proprietary software" or "non-free software".

The first formal definition of free software was published by FSF in February 1986. That definition, written by Richard Stallman, is still maintained today and states that software is free software if people who receive a copy of the software have the following four freedoms.

• Freedom 0: The freedom to run the program for any purpose.
• Freedom 1: The freedom to study how the program works, and change it to make it do what you wish.
• Freedom 2: The freedom to redistribute copies so you can help your neighbor.
• Freedom 3: The freedom to improve the program, and release your improvements (and modified versions in general) to the public, so that the whole community benefits.