Definition and the Four Freedoms Free software

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diagram of free , nonfree software, defined free software foundation. left: free software, right: proprietary software, encircled: gratis software


the first formal definition of free software published fsf in february 1986. definition, written richard stallman, still maintained today , states software free software if people receive copy of software have following 4 freedoms. numbering begins zero, not spoof on common usage of zero-based numbering in programming languages, because freedom 0 not included in list, later added first in list considered important.



freedom 0: freedom run program purpose.
freedom 1: freedom study how program works, , change make wish.
freedom 2: freedom redistribute , make copies can neighbor.
freedom 3: freedom improve program, , release improvements (and modified versions in general) public, whole community benefits.

freedoms 1 , 3 require source code available because studying , modifying software without source code can range highly impractical impossible.


thus, free software means computer users have freedom cooperate whom choose, , control software use. summarize remark distinguishing libre (freedom) software gratis (zero price) software, free software foundation says: free software matter of liberty, not price. understand concept, should think of free in free speech , not in free beer . see gratis versus libre.


in late 1990s, other groups published own definitions describe identical set of software. notable debian free software guidelines published in 1997, , open source definition, published in 1998.


the bsd-based operating systems, such freebsd, openbsd, , netbsd, not have own formal definitions of free software. users of these systems find same set of software acceptable, see copyleft restrictive. advocate permissive free software licenses, allow others use software wish, without being legally forced provide source code. view permissive approach more free. kerberos, x11, , apache software licenses substantially similar in intent , implementation.








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