BSD Licenses
BSD licenses refer to a family of permissive free software licenses, known for imposing minimal restrictions on the use and distribution of covered software. This is in contrast to copyleft licenses, which have share-alike requirements that mandate derivative works be distributed under the same license. The original BSD license was associated with the Berkeley Software Distribution (BSD), an influential Unix-like operating system developed at the University of California, Berkeley.
Origin and Development
The history of BSD licenses begins with the creation of the Berkeley Software Distribution. In the 1970s, the University of California, Berkeley received a copy of the Unix operating system from AT&T. Professors and students at Berkeley improved and expanded upon the Unix system, incorporating numerous enhancements. This led to the development of the Berkeley Software Distribution (BSD).
License Variants
Original BSD License
The original BSD license was simple, requiring that all code retain the BSD license notice if redistributed in source code format or reproduce the notice if redistributed in binary format. This license included clauses that were later seen as problematic, such as the advertising clause, which required all advertising materials mentioning features or use of the software to include an acknowledgment of the software's origin.
Modified BSD License
The modified BSD license, sometimes referred to as the "New BSD License" or "3-clause BSD license," removed the advertising clause. It retains the other requirements, such as including the copyright notice and licensing terms in all copies of the software.
Simplified BSD License
The simplified BSD license, or "2-clause BSD license," streamlines further by retaining only two clauses. It essentially requires that the software's copyright notice and license terms be included in all redistributions, whether in source or binary form.
Comparison with Other Licenses
BSD licenses are often compared with other permissive licenses like the MIT License and the Apache License. Like the MIT License, BSD licenses allow for reuse within proprietary software, provided that the original copyright notice and license terms are maintained. The Apache License, while also permissive, includes additional requirements such as patent protection clauses.
Impact and Usage
BSD licenses have had a significant impact on the development of open-source software. They are favored for their simplicity and permissive nature, allowing for wide adoption and integration into other projects. The ISC License, which is functionally equivalent to simplified BSD licenses, is endorsed by the OpenBSD project as a license template for new contributions.
The effects of BSD licenses are apparent in the widespread use of BSD-derived systems and tools. For example, the legal conflict known as UNIX System Laboratories, Inc. v. Berkeley Software Design, Inc. highlighted the significance of BSD in the broader Unix ecosystem.