Free software

Free software or software libre 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 to prevent consumer-facing hardware manufacturers from preventing user modifications to their hardware.

In practice, for software to be distributed as free software, the human-readable form of the program (the source code) must be made available to the recipient along with a notice granting the above permissions. Such a notice is a "free software licence", or, in theory, could be a notice saying that the source code is released into the public domain.

The free software movement was conceived in 1983 by Richard Stallman to give the benefit of "software freedom" to computer users. From the late 1990s 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 "Software Freedom Law Center" was founded in 2005 to protect and advance FLOSS. The antonym of free software is "proprietary software" or "non-free software".

Free software is distinct from "freeware" which is proprietary software made available free of charge. Users usually cannot study, modify, or redistribute freeware.

Since free software may be freely redistributed, it is generally available at little or no cost. Free software business models are usually based on adding value such as support, training, customization, integration, or certification. At the same time, some business models which work with proprietary software are not compatible with free software, such as those that depend on a user paying for a licence in order to lawfully use a software product.

History
In the 1950s, 1960s, and 1970s, it was normal for computer users to have the freedoms that are provided by free software. Software was commonly shared by individuals who used computers and by hardware manufacturers who were glad that people were making software that made their hardware useful. In the 1970s and early 1980s, the software industry began using technical measures (such as only distributing binary copies of computer programs) to prevent computer users from being able to study and modify software. In 1980 copyright law was extended to computer programs.

In 1983, Richard Stallman, longtime member of the hacker community at the MIT Artificial Intelligence Laboratory, announced the GNU project, saying that he had become frustrated with the effects of the change in culture of the computer industry and its users. Software development for the GNU operating system began in January 1984, and the Free Software Foundation (FSF) was founded in October 1985. He developed a free software definition and the concept of "copyleft", designed to ensure software freedom for all.

The economic viability of free software has been recognised by large corporations such as IBM, Red Hat, and Sun Microsystems. Many companies whose core business is not in the IT sector choose free software for their Internet information and sales sites, due to the lower initial capital investment and ability to freely customize the application packages. Also, some non-software industries are beginning to use techniques similar to those used in free software development for their research and development process; scientists, for example, are looking towards more open development processes, and hardware such as microchips are beginning to be developed with specifications released under copyleft licenses (see the OpenCores project, for instance). Creative Commons and the free culture movement have also been largely influenced by the free software movement.

Naming
The FSF recommends using the term "free software" rather than "open source software" because that term and the associated marketing campaign focuses on the technical issues of software development, avoiding the issue of user freedoms. "Libre" is used to avoid the ambiguity of the word "free". However, amongst English speakers, libre is primarily only used within the free software movement.

Definition
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 and modify the program.
 * Freedom 2: The freedom to copy the program so you can help your neighbor.
 * Freedom 3: The freedom to improve the program, and release your improvements to the public, so that the whole community benefits.

Freedoms 1 and 3 require source code to be available because studying and modifying software without its source code is highly impractical.

Thus, free software means that computer users have the freedom to cooperate with whom they choose, and to control the software they use. To summarize this into a remark distinguishing libre (freedom) software from gratis (zero price) software, Richard Stallman said: "Free software is a matter of liberty, not price. To understand the concept, you should think of 'free' as in 'free speech', not as in 'free beer ' ".

In the late 90s, other groups published their own definitions which describe an almost identical set of software. The most notable are Debian Free Software Guidelines published in 1997, and the Open Source Definition, published in 1998.

The BSD-based operating systems, such as FreeBSD, OpenBSD, and NetBSD, do not have their own formal definitions of free software. Users of these systems generally find the same set of software to be acceptable, but sometimes see copyleft as restrictive. They generally advocate permissive free software licenses, which allow others to make software based on their source code, and then release the modified result as proprietary software. Their view is that this permissive approach is more free. The Kerberos, X.org, and Apache software licenses are substantially similar in intent and implementation. All of these software packages originated in academic institutions interested in wide technology transfer (University of California, MIT, and UIUC).

Examples of free software
The Free Software Directory is a free software project that maintains a large database of free software packages.

Notable free software

 * GUI related
 * X Window System
 * GNOME
 * KDE
 * Xfce desktop environments
 * OpenOffice.org office suite
 * Firefox web browser.
 * Thunderbird email client.
 * Shareaza is free software multi-network peer-to-peer file sharing (P2P) client.
 * Typesetting and document preparation systems
 * TeX
 * LaTeX
 * Graphics tools
 * GIMP raster drawing and image editor
 * Inkscape vector graphic editor
 * Paint.NET raster drawing and image editing program
 * Blender 3D animation program
 * Text editors like vi or emacs.
 * Ogg is a free software multimedia container, used to hold Vorbis or Speex audio and Theora video.
 * Relational database systems
 * MySQL
 * PostgreSQL
 * GCC compilers, GDB debugger and the GNU C Library.

Compilers and interpreters
The tools needed to turn human-written source code into machine-executable programs are called compilers or interpreters. For some languages, such as C, C++, Common Lisp, Fortran, Tcl, Java, and Pascal, there are free and non-free compilers. For other languages, there is just one (or primarily one) compiler, and it is free software. This is the case for Perl, PHP, Python, Lua, and Ruby.

Servers

 * Apache web server
 * BIND name server
 * Sendmail mail transport
 * Samba file server.

Operating systems

 * GNU
 * Linux
 * BSD
 * Darwin
 * OpenSolaris

100% Free GNU/Linux distributions

 * BLAG Linux and GNU
 * dyne:bolic
 * gNewSense
 * GNUstep Live
 * Musix GNU+Linux
 * Ututo
 * Trisquel

Free software licenses
All free software licenses must grant people all the freedoms discussed above. However, unless the applications' licenses are compatible, combining programs by mixing source code or directly linking binaries is problematic, because of license technicalities. Programs indirectly connected together may avoid this problem.

The majority of free software uses a small set of licenses. The most popular of these licenses are:


 * the GNU General Public License
 * the GNU Lesser General Public License
 * the BSD License
 * the Mozilla Public License
 * the MIT License
 * the Apache License

The Free Software Foundation and the Open Source Initiative both publish lists of licenses that they find to comply with their own definitions of free software and open-source software respectively.


 * List of FSF approved software licenses
 * List of OSI approved software licenses

These lists are necessarily incomplete, because a license need not be known by either organization in order to provide these freedoms.

Apart from these two organizations, the Debian project is seen by some to provide useful advice on whether particular licenses comply with their Debian Free Software Guidelines. Debian doesn't publish a list of approved licenses, so its judgments have to be tracked by checking what software they have allowed into their software archives. That is summarized at the Debian web site.

However, it is rare that a license is announced as being in-compliance by either FSF or OSI guidelines and not vice versa (the Netscape Public License used for early versions of Mozilla being an exception), so exact definitions of the terms have not become hot issues.

Permissive and copyleft licenses
The FSF categorizes licenses in the following ways:


 * Public domain software - the copyright has expired, the work was not copyrighted or the author has abandoned the copyright. Since public-domain software lacks copyright protection, it may be freely incorporated into any work, whether proprietary or free.
 * Permissive licenses, also called BSD-style because they are applied to much of the software distributed with the BSD operating systems. The author retains copyright solely to disclaim warranty and require proper attribution of modified works, but permits redistribution and modification in any work, even proprietary ones.
 * Copyleft licenses, the GNU General Public License being the most prominent. The author retains copyright and permits redistribution and modification provided all such redistribution is licensed under the same license. Additions and modifications by others must also be licensed under the same 'copyleft' license whenever they are distributed with part of the original licensed product.

Security and reliability
There is debate over the security of free software in comparison to proprietary software, with a major issue being security through obscurity. A popular quantitative test in computer security is to use relative counting of known unpatched security flaws. Generally, users of this method advise avoiding products which lack fixes for known security flaws, at least until a fix is available. Some claim that this method is biased by counting more vulnerabilities for the free software, since its source code is accessible and its community is more forthcoming about what problems exist.

Free software advocates rebut that even if proprietary software does not have "published" flaws, flaws could still exist and possibly be known to malicious users. The ability of users to view and modify the source code allows many more people to potentially analyse the code and possibly to have a higher rate of finding bugs and flaws than an average sized corporation could manage. Users having access to the source code also makes creating and deploying spyware far more difficult.

Adoption
Free software played a part in the development of the Internet, the World Wide Web and the infrastructure of dot-com companies. Free software allows users to cooperate in enhancing and refining the programs they use; free software is a pure public good rather than a private good. Companies that contribute to free software can increase commercial innovation amidst the void of patent cross licensing lawsuits. (See mpeg2 patent holders)

Under the free software business model, free software vendors may charge a fee for distribution and offer pay support and software customization services. Proprietary software uses a different business model, where a customer of the proprietary software pays a fee for a license to use the software. This license may grant the customer the ability to configure some or no parts of the software themselves. Often some level of support is included in the purchase of proprietary software, but additional support services (especially for enterprise applications) are usually available for an additional fee. Some proprietary software vendors will also customize software for a fee.

Free software is generally available at little to no cost and can result in permanently lower costs compared to proprietary software. With free software, businesses can fit software to their specific needs by changing the software themselves or by hiring programmers to modify it for them. Free software often has no warranty, and more importantly, generally does not assign legal liability to anyone. However, warranties are permitted between any two parties upon the condition of the software and its usage. Such an agreement is made separately from the free software license.

A report by Standish Group says that adoption of open source has caused a drop in revenue to the proprietary software industry by about $60 billion per year.