The BSD license is a class of extremely simple and very liberal licenses for computer software that was originally developed at the University of California at Berkeley (UCB). It was first used in 1980 for the Berkeley Source Distribution (BSD), also known as BSD UNIX, an enhanced version of the original UNIX operating system that was first written in 1969 by Ken Thompson at Bell Labs.
BSD restrictions can be summarized as:
(1) one should not claim that they wrote the software if they did not write it .
(2) one should not sue the developer if the software does not function as expected or as desired.
Some BSD licenses additionally include a clause that restricts the use of the name of the project (or the names of its contributors) for endorsing or promoting derivative works.
Besides the original license used in BSD, there are several derivative licenses that are 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.
Note: In all BSD licences as following, is the organization of the or just the , and is the year of the copyright. As published in BSD, is "Regents of the University of California", and is "University of California, Berkeley".
Examples of BSD-Style Licenses
Below are three examples of BSD-style licenses:
(1) The BSD license as it is used by the FreeBSD operating system.
(2) A BSD license as it is used by Sudo (a free utility program for Unix-like operating systems).
(3) A template of a BSD-style license that can be applied to any appropriate project.
Proprietary software licenses compatibility:
The BSD License allows proprietary use and allows the software released under the license to be incorporated into proprietary products. Works based on the material may be released under a proprietary license as closed source software
BSD Licenses Versus the GPL
The GPL (GNU General Public License) is by far the most widely used license for free software (i.e., software whose source code is available at no cost for anyone to use for any purpose). The Linux kernel (i.e., the core of the operating system) as well as much of the other software generally included in Linux distributions have been released under the terms of the GPL.
Although far fewer programs are released under BSD-style licenses, this class of licenses is disproportionately important because of the widespread use of BSD-licensed code in both free and proprietary operating systems.
Possibly the biggest difference between the GPL and BSD licenses is the fact that the former is a copyleft license and the latter is not. Copyleft is the application of copyright law to permit the free creation of derivative works but requiring that such works be redistributable under the same terms (i.e., the same license) as the original work.