Introduction
All eggs and associated code MUST include some form of license. Below is a brief description of various licenses and how to include them. This list is not meant to be complete; it is merely a description of some of the common licences in use and their meanings.
Egg metafile tagging
Licenses should be identified by their SPDX short identifier, where possible. A complete list of SPDX identifiers can be found at https://spdx.org/licenses/.
Examples: "BSD-3-Clause", "MIT", "GPL-2.0", "LGPL-2.1"
If a license has no SPDX identifier but is commonly known by initials, capitalize them. If a license consists of multiple words capitalize the first letter of each word.
Example: "Public Domain"
If multiple licenses apply, separate them by forward slashes.
Example: "Public Domain/MIT"
Common License Types
Public Domain
Public domain licenses disavow any form of copyright on the code. There must be a notice of a form similar to the one below included in the relevant files and documentation.
This code is written by YOUR-NAME and placed in the Public Domain. All warranties are disclaimed.
Note: If any form of copyright is retained to the code, it is NOT in the public domain.
Permissive Licenses
Permissive licenses grant free usage of the code for any purpose. They differ from Public Domain primarily by the retention of copyright by the owner(s). There are many permissive licenses, some popular ones are shown below.
MIT license (Identifier: "MIT")
Copyright YEAR COPYRIGHT-HOLDER Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
2-Clause BSD license (Identifier: "BSD-2-Clause")
This license is also known as "Simplified BSD license" or "FreeBSD license".
Copyright YEAR COPYRIGHT-HOLDER 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.
3-Clause BSD license (Identifier: "BSD-3-Clause")
This license is also known as "New BSD License" or "Modified BSD license".
Copyright YEAR COPYRIGHT-HOLDER 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.
Copyleft licenses
Copyleft licenses differ from permissive licenses by ensuring derivative software uses the same license. The main choice to be made is whether you want to use a permissive or a copyleft license. For more information about the most popular copyleft license see http://www.gnu.org/licenses/gpl.html. If the software is intended to run as a network service, there is the AGPL (the rationale behind this license can be found at https://www.gnu.org/licenses/why-affero-gpl.html). If you intend to use the GPL, LGPL, or AGPL, make sure that the SPDX identifier matches the exact chosen version.