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Free software

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The controversial term free software is used in various ways:

  1. any software which may be copied and used without payment (think free beer)
  2. software that can be copied, used, studied, modified, resold, etc., with few or no restritions (think free speech).

Various common definitions

first, software that can be acquired and used without cost, and second, software that is distributed under a license which grants the recipient the freedoms to use, copy, modify and distribute the software. Free software in the first sense, often called freeware, should be contrasted with shareware and adware. The remainder of this article discusses free software in the second sense.

Richard Stallman's Definition

Notable software author Richard Stallman, founder of the Free Software Foundation, has codified his philosophy of software freedom into a specific definition (see free software definition).

The freedom definition of "free software" has been mainly advocated by Richard Stallman's Free Software Foundation (FSF) starting in the 1980's. Adherents to this movement say they belong to the Free World. The FSF has produced a specific definition of the term; a software is "free" in this sense if it grants:

  1. the freedom to run the program for any purpose
  2. the freedom to study and modify the program
  3. the freedom to copy the program
  4. the freedom to redistribute modified or unmodified versions of the program

Numbers 2 requires access to the program's 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 traditional licenses which don't grant these freedoms. Usually, 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". Some advocate the use of the words "libre" and "gratis" to avoid the ambiguity of the English word "free". It is possible (though rare) that free software be sold; however, the buyer may then legally distribute copies for free.

There are many variations on free software:

  • 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.
  • "copyleft" licenses, the most prominent being the GPL. 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.

See free software licenses for more information.

Note that the original copyright owner of copyleft-licenced software can also make a modified version under their original copyright, and sell it under any licence 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.

A large, and ever-growing, amount of software is made available under free software licenses; observers of this trend (and adherents to it) often refer to this phenomenon as the free software movement. Notable free software projects include the Linux and BSD operating system kernels, the GCC compiler, 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 office suite, the Mozilla web browser 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 licences.

However, 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.

Open Source is a concept closely related to free software. A group of people who went on to form the Open Source Initiative (OSI) coined the term to attempt to avoid the ambiguity of the English word "free", and to bring a higher profile to the practical benefits of free software. Many people recognise a qualitative benefit to the software development process when a program's source code can be used, modified and redistributed freely by developers; this causes a pragmatic appreciation for free software licenses independent from ideological concerns.

The OSI places emphasis on the pragmatic benefits of access to the program's source code, rather than focusing on user and programmer freedoms. The distinction is subtle, but the FSF considers it significant enough to distance itself from the Open Source term (claiming that free software is the morally correct way to produce software, regardless of whether it produces technically superior software). In most cases, though, licenses which qualify as free software licenses also qualify as open source licenses, and vice versa, so often the two terms are used interchangeably and usually the same people are happy to work on the software regardless of the ideologies involved.


Glossary:

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