BSD 3-Clause License: Classic Permissive License

BSD 3-Clause "New" or "Revised" License

The BSD 3-Clause License is one of the oldest open source licenses, originating from the University of California, Berkeley in the 1980s. It is a permissive license similar to MIT but with an additional clause restricting use of the project name for endorsement.

The Three Clauses

1. Source redistribution — Redistributions of source code must retain the copyright notice, conditions list, and disclaimer
2. Binary redistribution — Redistributions in binary form must reproduce the copyright notice in the documentation
3. Non-endorsement — Neither the name of the copyright holder nor the names of contributors may be used to endorse or promote derived products without written permission

Key Characteristics

Attribute	Value
SPDX Identifier	BSD-3-Clause
Type	Permissive
Patent Grant	No explicit grant
Copyleft	No

BSD-3-Clause vs BSD-2-Clause

BSD-2-Clause (the "Simplified" BSD license) removes the third clause about non-endorsement, making it even more permissive and nearly identical to MIT. BSD-3-Clause is preferred when you want explicit protection against others using your name to promote derivative works.

BSD-3-Clause vs MIT

Both are permissive and functionally similar. The main difference is the non-endorsement clause in BSD-3-Clause. MIT is shorter and simpler, which is why many modern projects prefer it. However, BSD-3-Clause has a longer track record in academic and systems programming contexts.

Notable Projects

• FreeBSD operating system
• Go standard library (parts)
• Many BSD-derived networking tools
• Academic research software