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The term free software refers to 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.
Programmers and developers in the 1960s and 1970s frequently shared their software in a manner similar to the principles of free software. 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 [1].
Stallman 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 proprietisation [2].
The FSF has produced a specific free software definition, by which software is "free" in this sense if it grants:
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 CDsCD re-directs here; see Cd for other meanings of CD . A compact disc (or CD is an optical disc used for storing digital data. It was originally invented for digital audio and is also used as a data storage device, a CD-ROM. CD-ROM reading devices are a st of free software such as Linux distributionA Linux distribution or GNU/Linux distribution (or a distro is a Unix-like operating system plus application software comprising the Linux kernel, the GNU operating system, assorted free software and sometimes proprietary software, all created by individus 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 movementThe free-software movement began in 1983 when Richard Stallman announced the GNU project. The goal of the movement is to give freedom to computer users by replacing software which has restrictive licensing terms with free software ( free as in freedom). and are only slowly spreading to the outside world. Others advocate the term open source software, but the relationship between "open source" and "free software" is complex.
There are several variations on free software in the FSF sense, for example:
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.