The BSD license is an acronym for the Berkeley Software Distribution license agreement, and is one of the most widely used licenses for free software (a subset of open source software). Many software programs are released under this license including BSD software (largely, a version of UNIX) for which the license was named.
The owner of the original BSD distribution was the "Regents of the University of California". This is because BSD originally came from the University of California, Berkeley. The official BSD license has been revised since its inception, and has inspired numerous variants used by others to license their software programs (see "BSD-style licenses" section below).
This license has few restrictions on it compared to other licenses such as the GNU General Public License or even the default restrictions provided by copyright, putting it relatively closer to the public domain. (Indeed, the BSD License has been referred to as copycenter, for comparison to both standard copyright and the GPL's copyleft: "Take it down to the copy center and make as many copies as you want.")
 Terms of the BSD license
The text of the license is considered to be in the public domain and thus may be modified without restriction. To suit the needs of a particular individual or organization, one should switch out the terms 'Regents of the University of California', 'University of California, Berkeley', and 'Regents' with their own name.
* Copyright (c) 1998, Regents of the University of California * 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. * * Neither the name of the University of California, Berkeley 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 REGENTS 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 REGENTS AND 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.
 Compatibility with proprietary software licenses
The BSD License allows proprietary commercial use, and for the software released under the license to be incorporated into proprietary commercial products. Works based on the material may even be released under a proprietary license. Some notable examples of this are the use of BSD networking code in Microsoft products, and the use of numerous FreeBSD components in Mac OS X.
It is possible for something to be distributed with the BSD License and some other license to apply as well. This was in fact the case with very early versions of BSD Unix itself, which included proprietary material from AT&T.
 Compatibility with other free software licenses
As originally written, the BSD license contained terms that made it incompatible  with the GNU General Public License (see the "advertising clause" section below). As these are among the most commonly-used licensing agreements for free and open source software, it was a serious problem for software authors to be unable to mix GPL and BSD components in their own projects. As of a revision to the BSD license in 1999, the controversial clause was removed. Since then, authors of free and open source software have been free to incorporate BSD-licensed software with GPL-licensed works.
 The UC Berkeley advertising clause
As originally distributed, the BSD license had an extra clause, requiring authors of all works deriving from a BSD-licensed work to include an acknowledgment of the original source. This is numbered as clause 3 in the original licence text:
* Copyright (c) 1982, 1986, 1990, 1991, 1993 * The Regents of the University of California. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. 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. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 4. Neither the name of the University 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 REGENTS 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 REGENTS 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.
The GNU project referred to it as the "obnoxious BSD advertising clause". There were two main problems from the GNU project's perspective. First, people who made changes to the source code tended to want to have their names added to the acknowledgement. This is problematic since with large numbers of people working on a single project (or for many separate projects in a software distribution), the advertising clause quickly created large and unwieldy acknowledgements. Second, a large legal problem was the advertising clause was incompatible with the terms of the GNU General Public License (which does not allow the addition of restrictions beyond those it already imposes) thus forcing a segregation of GNU and BSD software. The GNU project went so far as to suggest people not use the phrase "BSD-style" licensing when they wanted to refer to an example of a non-copyleft license, in order to prevent inadvertent usage of the original BSD license.
This '4-clause' advertising version was removed from the official BSD license text on July 22, 1999 by William Hoskins, the director of the office of technology licensing for Berkeley, in response to a request from Richard Stallman. The document enacting that revocation is available at
The original license is now sometimes called "BSD-old" or "4-clause BSD", while the current revision of the BSD license is sometimes referred to by the by names including "BSD-new", "revised BSD", or "3-clause BSD".
 BSD-style licenses
Several free or open source licenses that derive from or are similar to the BSD license are widely used:
- NetBSD still uses a 4-clause license equivalent to the original BSD license.
- A 2-clause BSD-like license also exists which deletes the third clause, prohibiting use of the copyright holder's name for endorsement purposes. Removal of that clause makes the license functionally equivalent to the MIT License. This is the only BSD-style license permitted for certain libraries included in KDE.
- FreeBSD also uses a 2-clause license with an additional statement at the end that the views of contributors are not the official views of the FreeBSD Project.
- OpenBSD uses a license modeled after the ISC license for all additional software created by the project, as it is functionally a two-clause BSD-styled license, with no additional clauses or consequences involved.
- SixXS uses an extended 3-clause BSD [LICENSE], the license contains a short list of the differences compared to the 3 clause BSD license. 'Written' permission has been removed from the 3rd clause, email suffices. 2 clauses added which requires that no logo's or texts are removed, which is similar to the 1st clause. The 5th clause makes a request to notify the authors when one is using this software for alternate purposes than SixXS. The latter is mainly of interrest because the AICCU software is written with SixXS in mind and not with other providers. If somebody thus makes an interoperable server, using the protocols that have been specified, they would be happy to know about this.
 See also
 External links
- BSD License Template
- The BSD License Problem (GNU Project) (This article is mostly outdated, because of the license change in 1999.)
- Materials about the Unix System Laboratories v. BSD case
- Marshall Kirk McKusick, Twenty Years of Berkeley Unix: From AT&T-Owned to Freely Redistributable, in: Open Sources: Voices from the Open Source Revolution, O'Reilly 1999
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