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BSD licenses are a family of permissive free software licenses, imposing minimal restrictions on the use and distribution of covered software. This is in contrast to
copyleft Copyleft is the practice of granting the right to freely distribute and modify intellectual property with the requirement that the same rights be preserved in derivative works created from that property. Copyleft in the form of licenses can be u ...

copyleft
licenses, which have
share-alike The copyleft.html"_;"title="Creative_Commons_icon_for_Share-Alike,_a_variant_of_the_copyleft">Creative_Commons_icon_for_Share-Alike,_a_variant_of_the_copyleft_symbol Share-alike_is_a_Copyright.html" ;"title="copyleft_symbol.html" ;"title="copylef ...
requirements. The original BSD license was used for its namesake, the
Berkeley Software Distribution The Berkeley Software Distribution (BSD) is a discontinued operating system An operating system (OS) is system software that manages computer hardware, computer software, software resources, and provides common daemon (computing), services f ...
(BSD), a
Unix-like A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-like Ap ...
operating system An operating system (OS) is system software that manages computer hardware, computer software, software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), sch ...

operating system
. The original version has since been revised, and its descendants are referred to as modified BSD licenses. BSD is both a license and a class of license (generally referred to as BSD-like). The modified BSD license (in wide use today) is very similar to the license originally used for the BSD version of
Unix Unix (; trademarked as UNIX) is a family of multitasking, multiuser Multi-user software is computer software Software is a collection of Instruction (computer science), instructions and data (computing), data that tell a computer how to ...
. The BSD license is a simple license that merely requires that all code retain the BSD license notice if redistributed in source code format, or reproduce the notice if redistributed in binary format. The BSD license (unlike some other licenses e.g.
GPL The GNU General Public License (GNU GPL or simply GPL) is a series of widely used free software license A free-software license is a notice that grants the recipient of a piece of software extensive rights to modify and redistribute that ...
) does not require that source code be distributed at all.


Terms

In addition to the original (4-clause) license used for BSD, several derivative licenses have emerged that are also commonly referred to as a "BSD license". Today, the typical BSD license is the 3-clause version, which is revised from the original 4-clause version. In all BSD licenses as following, is the year of the copyright. As published in BSD, is "Regents of the University of California".


Previous license

Some releases of BSD prior to the adoption of the 4-clause BSD license used a license that is clearly ancestral to the 4-clause BSD license. These releases include some parts of 4.3BSD-Tahoe (1988), about 1000 files, and Net/1 (1989). Although largely replaced by the 4-clause license, this license can be found in 4.3BSD-Reno, Net/2, and 4.4BSD-Alpha.
Copyright (c) . All rights reserved. Redistribution and use in source and binary forms are permitted provided that the above copyright notice and this paragraph are duplicated in all such forms and that any documentation, advertising materials, and other materials related to such distribution and use acknowledge that the software was developed by the . The name of the may not be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED ``AS IS AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.


4-clause license (original "BSD License")

The original BSD license contained a clause not found in later licenses, known as the "advertising clause". This clause eventually became controversial, as it required authors of all works deriving from a BSD-licensed work to include an acknowledgment of the original source in all advertising material. This was clause number 3 in the original license text:
Copyright (c) , All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: #Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. # Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. #All advertising materials mentioning features or use of this software must display the following acknowledgement: This product includes software developed by the . #Neither the name of the nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY ''AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
This clause was objected to on the grounds that as people changed the license to reflect their name or organization it led to escalating advertising requirements when programs were combined in a software distribution: every occurrence of the license with a different name required a separate acknowledgment. In arguing against it,
Richard Stallman Richard Matthew Stallman (; born March 16, 1953), also known by his initials, rms, is an American free software movement activist and programmer A computer programmer, sometimes called a software developer, a programmer or more recently a ...

Richard Stallman
has stated that he counted 75 such acknowledgments in a 1997 version of
NetBSD NetBSD is a free and open-source Free and open-source software (FOSS) is software Software is a collection of Instruction (computer science), instructions and data (computing), data that tell a computer how to work. This is in contrast t ...

NetBSD
. In addition, the clause presented a legal problem for those wishing to publish BSD-licensed software which relies upon separate programs using the
GNU GPL The GNU General Public License (GNU GPL or simply GPL) is a series of widely-used free software licenses that guarantee end users the freedom to run, study, share, and modify the software. The licenses were originally written by Richard Stallma ...
: the advertising clause is
incompatible Compatibility may refer to: Computing * Backward compatibility, in which newer devices can understand data generated by older devices * Compatibility card, an expansion card for hardware emulation of another device * Compatibility layer, compone ...
with the GPL, which does not allow the addition of restrictions beyond those it already imposes; because of this, the GPL's publisher, the
Free Software Foundation The Free Software Foundation (FSF) is a 501(c)(3) non-profit organization founded by Richard Stallman on October 4, 1985, to support the free software movement, which promotes the universal freedom to study, distribute, create, and modify compu ...
, recommends developers not use the license, though it states there is no reason not to use software already using it. Today, this original license is now sometimes called "''BSD-old''" or "''4-clause BSD''".


3-clause license ("BSD License 2.0", "Revised BSD License", "New BSD License", or "Modified BSD License")

The advertising clause was removed from the license text in the official BSD on by William Hoskins, Director of the Office of Technology Licensing for UC Berkeley. Other BSD distributions removed the clause, but many similar clauses remain in BSD-derived code from other sources, and unrelated code using a derived license. While the original license is sometimes referred to as the "BSD-old", the resulting 3-clause version is sometimes referred to by "BSD-new." Other names include "New BSD", "revised BSD", "BSD-3", or "3-clause BSD". This version has been vetted as an Open source license by the OSI as "The BSD License". The Free Software Foundation, which refers to the license as the "Modified BSD License", states that it is compatible with the GNU GPL. The FSF encourages users to be specific when referring to the license by name (i.e. not simply referring to it as "a BSD license" or "BSD-style") to avoid confusion with the original BSD license. This version allows unlimited redistribution for any purpose as long as its copyright notices and the license's disclaimers of warranty are maintained. The license also contains a clause restricting use of the names of contributors for endorsement of a derived work without specific permission.
Copyright Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: #Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. #Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. #Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.


2-clause license ("Simplified BSD License" or "FreeBSD License")

An even more simplified version has come into use, primarily known for its usage in
FreeBSD FreeBSD is a free and open-source Free and open-source software (FOSS) is software Software is a collection of Instruction (computer science), instructions and data (computing), data that tell a computer how to work. This is in contrast ...

FreeBSD
. It was in use there as early as April 29, 1999 and likely well before. The primary difference between it and the New BSD (3-clause) License is that it omits the non-endorsement clause. The FreeBSD version of the license also adds a further disclaimer about views and opinions expressed in the software, though this is not commonly included by other projects. The Free Software Foundation, which refers to the license as the FreeBSD License, states that it is compatible with the GNU GPL. In addition, the FSF encourages users to be specific when referring to the license by name (i.e. not simply referring to it as "a BSD license" or "BSD-style"), as it does with the modified/new BSD license, to avoid confusion with the original BSD license.
Copyright (c) , Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: # Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. # Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Other projects, such as NetBSD, use a similar 2-clause license. This version has been vetted as an Open source license by the OSI as the "Simplified BSD License." The
ISC license The ISC license is a Permissive software licence, permissive free software license published by the Internet Software Consortium, nowadays called Internet Systems Consortium (ISC). It is functionally equivalent to the BSD licenses#2-clause, sim ...
is functionally equivalent, and endorsed by the
OpenBSD OpenBSD is a security-focused, free and open-source Free and open-source software (FOSS) is software Software is a collection of Instruction (computer science), instructions and data (computing), data that tell a computer how to work. T ...
project as a license template for new contributions.


0-clause license ("BSD Zero Clause License")

The BSD 0-clause license goes further than the 2-clause license by dropping the requirements to include the copyright notice, license text, or disclaimer in either source or binary forms. Doing so forms a
public-domain-equivalent license Public-domain-equivalent license are licenses that grant public-domain-like rights and/or act as waiver A waiver is the voluntary wikt:relinquishment, relinquishment or Surrender (law), surrender of some known Rights, right or privilege. Regu ...
, the same way as MIT No Attribution License. It is known as "0BSD", "Zero-Clause BSD", or "Free Public License 1.0.0". It was first used by Rob Landley in
Toybox Toybox is a free and open-source software Free and open-source software (FOSS) is software Software is a collection of Instruction (computer science), instructions and data (computing), data that tell a computer how to work. This is in con ...
.
Copyright (C)
ear The ear is the organ of hearing and, in mammals, balance. In mammals, the ear is usually described as having three parts—the outer ear The outer ear, external ear, or auris externa is the external part of the ear, which consists ...

ear
by opyright holder<
mail The mail or post is a system for physically transporting postcards, letters, and parcels. A postal service can be private or public, though many governments place restrictions on private systems. Since the mid-19th century, national postal sy ...

mail
Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted. THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.


Other variations

The
SPDX Software Package Data Exchange (SPDX) is a file format ogg-file: 154 kilobytes. A file format is a standard way that information is encoded for storage in a computer file. It specifies how bits are used to encode information in a digital st ...
License List contains extra BSD license variations. Examples include: * , a license with only the source code retaining clause. * , a variation of BSD-2-Clause with a patent grant. * , a variation of BSD-3-Clause that adds a disclaimer that a piece of software is not designed for use in a
nuclear facility A nuclear power plant (sometimes abbreviated as NPP) is a thermal power station in which the heat source is a nuclear reactor. As is typical of thermal power stations, heat is used to generate steam that drives a steam turbine A steam turbine i ...
.


License compatibility


Commercial license compatibility

The FreeBSD project argues on the advantages of BSD-style licenses for companies and commercial use-cases due to their license compatibility with
proprietary {{Short pages monitor