- This article is about free software as defined by the Free Software Foundation. For software available free of charge, see Freeware.
Free software is software which, once obtained, can be used, copied, studied, modified and redistributed. It is often made available online without charge or offline for the cost of distribution; however, this is not required, and software can be "free as in free speech" and sold for profit. Similarly, freeware is sometimes published with source code; however, the software is not free in the same sense as free software unless the rights to modify and redistribute modified versions of the program are guaranteed.
In the 1960s and 1970s, software was not considered to be a product but rather an addon the mainframe vendors gave to their customers to use the computers at all. In that culture, programmers and developers frequently shared their software freely among each other. This was especially common with some of the large users groups, such as DECUS, the DEC (Digital Equipment Corporation) Users Group. In the late 1970s, companies started routinely imposing restrictions on users with the use of license agreements.
In 1984, Richard Stallman started working on the GNU project, founding the Free Software Foundation (FSF) one year later  (http://www.gnu.org/fsf/fsf.html). He introduced a definition for "free software" and the concept of "copyleft", which he specifically devised to give users freedom and to restrain the possibilities for appropriation  (http://cisn.metu.edu.tr/2002-6/free.php).
According to that definition, software is "free" if it grants:
- the freedom to run the program for any purpose (called "freedom 0")
- the freedom to study and modify the program ("freedom 1")
- the freedom to copy the program so you can help your neighbor ("freedom 2")
- the freedom to improve the program, and release your improvements to the public, so that the whole community benefits ("freedom 3")
Note that freedoms 1 and 3 require access to the source code.
A list of compliant licenses is available from FSF's web site (see below). The term "proprietary software" is used for software distributed under more restrictive licenses which do not grant these freedoms. Copyright law reserves most rights of modification, duplication and redistribution for the copyright owner; software released under a free software license specifically rescinds most of these reserved rights.
The FSF definition of free software does not touch on the issue of price; a commonly used slogan is "free as in speech, not as in beer", and it is common to see CDs of free software such as Linux distributions for sale. However, in this situation the buyer of the CD would have the right to copy and redistribute it. Free beer software can include restrictions that do not conform to the FSF definition — for example, gratis software may not include source code, may actively prohibit redistributors from charging a fee, etc.
To avoid confusion, some people use the words "libre" and "gratis" to avoid the ambiguity of the English word "free". However, these alternative terms are still used mostly within the free software movement and are only slowly spreading to the outside world.
Others advocate the term open source software. However, according to the FSF, the Open Source movement is philosophically distinct from the free software movement. See the discussion below (Comparison with Open Source software).
There are several variations on free software in the FSF sense, for example:
- The freedoms defined by the FSF are protected through copyleft licenses, the most prominent of which is the GNU General Public License. The author retains copyright, and permits redistribution and modification under terms designed to ensure that all modified versions of the software remain under copyleft terms.
- Public domain software, in which the author has abandoned the copyright. Public-domain software, since it is not protected by copyright at all, may be freely incorporated into closed, proprietary works as well as free ones.
- BSD-style licenses, so called because they are applied to much of the software distributed with the BSD operating systems. The author under such licenses retains copyright protection solely to disclaim warranty and to require proper attribution of modified works, but permits redistribution and modification, even in proprietary works.
Note that the original copyright owner of copyleft-licensed software can also make a modified version under their original copyright, and sell it under any license they like, in addition to distributing the original version as free software. This technique has been used as a business model by a number of free software companies; this does not restrict any of the rights granted to the users of the copyleft version.
Examples and evolution
A large and increasing amount of software is made available under free software licenses; observers of this trend (and adherents) often refer to this phenomenon as the free software movement. Notable free software projects include the Linux and BSD operating system kernels, the GCC compilers, GDB debugger and C libraries, the BIND name server, the Sendmail mail transport server, the Apache web server, the MySQL and PostgreSQL relational database systems, the Perl, Python, Tcl and PHP programming languages, the X Window System, the GNOME and KDE desktop environments, the OpenOffice.org office suite, the Mozilla web browser, the Samba file server system, and the GIMP graphics editor.
Like all free software, these projects distribute their programs under licenses that grant users all the freedoms discussed above, but because of technicalities in the licenses, combining programs by mixing source code or directly linking binaries may be problematic unless both applications are under mutually compatible licenses. When programs are not directly linked together into a single program, these problems do not exist. Much free software can run on non-free platforms such as Microsoft Windows, and non-free software can be run on free platforms, although purists prefer to use all-free software running on a free platform such as Linux.
Free software packages constitute a software ecosystem where different pieces of software can provide services to one another, leading to co-evolution of features: in one simple example, the Python programming language provides support for the HTTP protocol, and the Apache web server that provides the HTTP protocol can call the Python programming language to serve dynamic content.
The Debian Project, which produces an operating system entirely composed of free software, created a set of guidelines that are used to evaluate the compatibility of a license with Debian's free-ness goal. The Debian Free Software Guidelines are used to delineate the free from non-free software. Debian had by 2003 collected over seven and a half thousand software packages compliant with the above guidelines.
Debian developers also argue that the same principles should apply not only to programs, but to software documentation as well. Many documents written by the Linux Documentation Project, and many documents licensed under the GNU Free Documentation License (the documents with invariant sections), do not comply with all of the above guidelines.
Comparison with Open Source software
While on practical level Open Source Software and Free Software share the same licenses, according to the FSF, the Open Source movement is philosophically distinct from the free software movement. It began in 1998 with a group of people, notably Eric S. Raymond and Bruce Perens, who formed the Open Source Initiative (OSI). They sought to (1) bring a higher profile to the practical benefits of sharing software source code, and (2) to interest major software houses and other high-tech industry companies in the concept. These advocates see the term open source as avoiding the ambiguity of the English word "free" in free software. The term "open source" was coined by Christine Peterson of the Foresight Institute think tank. It was registered to act as a trade mark for free software products.
Many people recognise a qualitative benefit to the software development process when a program's source code can be used, modified and redistributed by developers. (See also The Cathedral and the Bazaar.) The free software movement places primary emphasis on the moral or ethical aspects of software, seeing technical excellence as a desirable by-product of its ethical standard. The Open Source movement sees technical excellence as the primary goal, regarding source code sharing as a means to an end. As such, the FSF distances itself both from the Open Source movement and from the term "Open Source".
Since the OSI only approves free software licenses as complying with the OSD, most people interpret it as a distribution scheme, and freely interchange "open source" with "free software". Even though there are important philosophical differences between the two terms, particularly in terms of the motivations for developing and using such software, they seldom make any impact in the collaboration process.
Whilst the term "Open Source" removes the ambiguity of Freedom versus Price, it introduces another: between programs that meet the Open Source Definition, giving users the freedom to improve upon them, and programs that simply have source available, possibly with heavy restrictions on the use of that source. Many people believe that any software that has source available is open source because they can tinker with it themselves. (An example of such software would have been the popular formerly-proprietary but source-included freeware package Graphviz, but AT&T went and changed the licence.) However, much of this software does not give its users the freedom to distribute their modifications, restricts commercial usage, or otherwise restricts users' rights.
Once a free software product has started to circulate, it soon becomes available at little or no cost. At the same time, its utility does not decrease. This means that free software can be characterized as a pure public good rather than a private good.
Since free software allows free use, modification, and distribution, it often finds a home in third world countries for whom the cost of proprietary software is sometimes prohibitive. It is also easily modified locally, so translation efforts into languages which are not necessarily commercially profitable are also feasible. See also internationalization.
Most free software is produced by international teams cooperating through free association. Teams typically are composed of individuals with a wide variety of motivations. There are many stances about the relation of free software to the current, capitalist economic system:
- Some consider free software to be a competitor to capitalism.
- Some consider free software to be another form of competition within free markets, and that copyright is a governmental restriction on the market.
- Some compare free software to a gift economy, where a person's worth is based on what they give away
- Groups like Oekonux and Hipatia consider that everything could be produced in this manner and that this model of production isn't limited to superseding the proprietary model of software development. Cooperation based on free association can be and is used for other purposes (such as writing encyclopedias and give-away shops).
There is a controversy about the relative security of free software vs. proprietary software (one of the major issue being security through obscurity). A commonly used method to determine the relative security of the products is to determine how many unpatched security flaws are in each of the products involved. It is generally advised by users of this method that when a product provides no way to patch known security flaws, don't use it at least until the fix is available.
As of early December, 2004 the security site Secunia.com (http://secunia.com) counts zero security flaws unpatched (not yet fixed) for the most commonly used free software products for internet browsing, office productivity, and e-mail - Mozilla Firefox, OpenOffice.org and Mozilla Thunderbird, as compared to several security flaws not yet fixed for each of the three main proprietary (Microsoft-made) equivalent software products - Internet Explorer, Microsoft Office and Outlook Express.
External links and references