> For the complete documentation index, see [llms.txt](https://book.bsdcn.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://book.bsdcn.org/ask/flat/chapter-3-migration-guide/di-3.5-jie-bsd-xu-ke-zheng-gai-lan.md). # 3.5 Overview of BSD Licenses The BSD license is an important category of free software licenses with relatively permissive terms of use. This document lists the major BSD licenses, including those approved by the OSI (Open Source Initiative), as well as the historically significant but OSI-unapproved BSD-4-Clause. For more BSD license information, see OSI. All BSD licenses listed below are non-copyleft licenses, meaning they do not require modified derivative versions to be released as free software. The clause numbers of BSD licenses indicate the complexity of additional obligations and restrictions. 0BSD has the fewest restrictions, while BSD-4-Clause has the most. ## The Zero-Clause BSD License (0BSD) The Zero-Clause BSD License is the least restrictive among the BSD license family. Although named "BSD," it does not actually originate from the traditional BSD family. This license is a variant of the ISC license. The ISC license originated from the Internet Software Consortium (later renamed Internet Systems Consortium) and is a concise permissive license; 0BSD is approximately equivalent to a public domain license. Full text: ``` Zero-Clause BSD ============= 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. ``` Unofficial translation: ``` Zero-Clause BSD License Permission is hereby granted to anyone to use, copy, modify, and/or distribute this software for any purpose, whether or not a fee is charged. This software is provided "as is," and the author makes no warranties regarding 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. ``` ## The 1-Clause BSD License (BSD-1-Clause) The 1-Clause BSD License adds a copyright notice requirement on top of the zero-clause license. Full text: ``` Copyright (c) [Year] [Organization Name] [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. THIS SOFTWARE IS PROVIDED BY [Name of Organization] "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 [Name of Organization] 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. ``` Unofficial translation: ``` Copyright (c) [Year] [Organization Name] 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. This software is provided by [Organization Name] "as is," without any express or implied warranties, including but not limited to the implied warranties of merchantability and fitness for a particular purpose. In no event shall [Organization Name] be liable for any direct, indirect, incidental, special, punitive, or consequential damages (including but not limited to procurement of substitute goods or services, loss of use, data, or profits, or business interruption) arising from the use of this software, regardless of the theory of liability, whether in contract, strict liability, or tort (including negligence or otherwise), even if advised of the possibility of such damage. ``` ## The 2-Clause BSD License (BSD-2-Clause) The 2-Clause BSD License is widely used and is the FreeBSD license, also known as the Simplified BSD License, preferred by the FreeBSD project. This license removed the advertising clause and endorsement clause from the original BSD license (BSD-4-Clause), requiring only that the copyright notice, list of conditions, and disclaimer be retained in source code and binary redistributions. The advertising clause originally required that all advertising materials mentioning the features or use of this software acknowledge the use of software developed by the original author; it has been removed due to its impracticality in actual use. Full text: ``` Copyright 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. 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. ``` Unofficial translation: ``` Copyright 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. This software is provided by the copyright holders and contributors "as is," without any express or implied warranties, including but not limited to the implied warranties of merchantability and fitness for a particular purpose. In no event shall the copyright holders or contributors be liable for any direct, indirect, incidental, special, punitive, or consequential damages (including but not limited to procurement of substitute goods or services, loss of use, data, or profits, or business interruption) arising from the use of this software, regardless of the theory of liability, whether in contract, strict liability, or tort (including negligence or otherwise), even if advised of the possibility of such damage. ``` ## The 3-Clause BSD License (BSD-3-Clause) The 3-Clause BSD License adds a restriction on using the author's name for promotion on top of the two-clause license. The 3-Clause BSD License is also known as the New BSD License or Modified BSD License. This license removed the advertising clause from the original BSD license (i.e., BSD-4-Clause) and additionally restricts the use of the author's name to endorse or promote derived products. Full text: ``` Copyright 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. 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. ``` Unofficial translation: ``` Copyright 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. Without specific prior written permission, the names of the copyright holders or contributors may not be used to endorse or promote products derived from this software. This software is provided by the copyright holders and contributors "as is," without any express or implied warranties, including but not limited to the implied warranties of merchantability and fitness for a particular purpose. In no event shall the copyright holders or contributors be liable for any direct, indirect, incidental, special, punitive, or consequential damages (including but not limited to procurement of substitute goods or services, loss of use, data, or profits, or business interruption) arising from the use of this software, regardless of the theory of liability, whether in contract, strict liability, or tort (including negligence or otherwise), even if advised of the possibility of such damage. ``` ## BSD 4-Clause "Original" or "Old" License (BSD-4-Clause) The 4-Clause BSD License is the original version of the BSD license with more restrictive conditions. The 4-Clause BSD License is the original BSD license and is currently not approved by the OSI. This license includes an advertising clause requiring that all advertising materials mentioning the features or use of this software acknowledge the use of products developed by the original author (see Clause 3 below). Full 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: 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 organization. 4. 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 COPYRIGHT HOLDER "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 COPYRIGHT HOLDER 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. ``` Unofficial translation: ``` Copyright . 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 organization. 4. Without specific prior written permission, the names of the copyright holders or contributors may not be used to endorse or promote products derived from this software. This software is provided by the copyright holder "as is," without any express or implied warranties, including but not limited to the implied warranties of merchantability and fitness for a particular purpose. In no event shall the copyright holder be liable for any direct, indirect, incidental, special, punitive, or consequential damages (including but not limited to procurement of substitute goods or services, loss of use, data, or profits, or business interruption) arising from the use of this software, regardless of the theory of liability, whether in contract, strict liability, or tort (including negligence or otherwise), even if advised of the possibility of such damage. ``` ## References * Open Source Initiative. OSI Approved Licenses\[EB/OL]. \[2026-04-17]. . OSI is the official certification body for open source software licenses, providing the most authoritative license approval and classification information. For more BSD license information, see . * SPDX. SPDX License List\[EB/OL]. \[2026-03-25]. . SPDX provides a standardized license identifier list. * FSF. Problems with the BSD License\[EB/OL]. \[2026-03-25]. . 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