| PLEP | 4 |
|---|---|
| author(s) | Nicholas A. Murphy |
| contact email | namurphy@cfa.harvard.edu |
| date created | 2017-09-28 |
| date last revised | 2018-09-26 |
| type | process |
| status | accepted |
| DOI | 10.5281/zenodo.1435990 |
The purpose of this PlasmaPy Enhancement Proposal (PLEP) is to clarify the licensing practices of PlasmaPy repositories. Source code files, code snippets, and associated documentation shall in general be covered by a BSD 3-clause license with an explicit patent grant. Other creative works shall in general be covered by the Creative Commons Attribution 4.0 International (CC BY 4.0) license. If back and forth collaboration with a body of work released under a copyleft license [e.g., the Creative Commons Attribution-ShareAlike (CC BY-SA 4.0) license] is desirable, then a PlasmaPy repository may be licensed under one or more compatible copyleft licenses. When PlasmaPy adopts or incorporates an existing body of creative works released under an Open Source Initiative (OSI) approved license or a Creative Commons license, then that body of work and its derivatives may continue to use that license. PlasmaPy’s Coordinating Committee may make exceptions to this policy when there are extenuating circumstances.
PlasmaPy began development under the permissive BSD 3-clause license. The primary advantage of this license is its compatibility with other licenses. Code released under a BSD license may be used by or incorporated into software covered by most permissive, copyleft, and proprietary licenses. The choice of this license allows back and forth sharing of code with projects such as Astropy and SunPy.
Most modern software licenses include language that protects against software patents. The BSD 3-clause license does not explicitly include such language. This oversight leaves potential for a contributor to patent their contribution, and then later prohibit use of their contribution by the PlasmaPy community. Plasma physics has a variety of commercial applications, so it is important to provide users with protections against software patents. On 2017 October 19, the patent grant from the BSD+Patent license was added to PlasmaPy’s license to give users the right to use contributions even if a contributor later patents their contribution. This clause covers all contributions made past this date, and the contributions made by people who have agreed to the clause. The patent clause grants users more rights and protections than the standard BSD 3-clause license.
Some PlasmaPy repositories contain creative works other than source code files, code snippets, and associated documentation. Creative Commons licenses are much more appropriate than open source licenses to cover these other creative works. Works released under the CC BY 4.0 license may be shared and adapted as long as attribution is provided. Works released under the copyleft CC BY-SA 3.0 or CC BY-SA 4.0 licenses may be shared and adapted as long as attribution is provided and derived works are covered by either the same license or a compatible license. The GNU Free Documentation License (GFDL) is another commonly used copyleft license.
CC BY and CC BY-SA licenses are compatible with each other in only one direction. Works released under a CC BY license may be adapted, redistributed, and relicensed under a CC BY-SA license with attribution. However, works released under a CC BY-SA license may not be adapted, redistributed, or relicensed under a CC BY license. Choosing a copyleft license is often appropriate when back and forth collaboration with existing bodies of work covered by a copyleft license is desirable. Care must be chosen to allow two-way licensing compatibility.
Software repositories created by PlasmaPy shall use the following BSD 3-clause license with the explicit patent grant from the OSI-approved BSD+Patent license. This license may be used for documentation internal to the project (e.g., documentation contained within a docs subdirectory).
Copyright (c) 2017-2525, PlasmaPy Developers.
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.
- 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.
- Neither the name of PlasmaPy nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.
Subject to the terms and conditions of this license, each copyright holder and contributor hereby grants to those receiving rights under this license a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable (except for failure to satisfy the conditions of this license) patent license to make, have made, use, offer to sell, sell, import, and otherwise transfer this software, where such license applies only to those patent claims, already acquired or hereafter acquired, licensable by such copyright holder or contributor that are necessarily infringed by:
- their Contribution(s) (the licensed copyrights of copyright holders and non-copyrightable additions of contributors, in source or binary form) alone; or
- combination of their Contribution(s) with the work of authorship to which such Contribution(s) was added by such copyright holder or contributor, if, at the time the Contribution is added, such addition causes such combination to be necessarily infringed. The patent license shall not apply to any other combinations which include the Contribution.
Except as expressly stated above, no rights or licenses from any copyright holder or contributor is granted under this license, whether expressly, by implication, estoppel or otherwise.
Disclaimer
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.
Creative works besides source code files, code snippets, and documentation contained within a docs directory shall by default be covered by the CC BY 4.0 license.
If significant collaboration with an existing body of creative work covered by a copyleft license is desired, then a PlasmaPy repository may be covered by one or more copyleft licenses that provide for two-way compatibility. In order for a work to be fully compatible with Wikipedia, for example, it must be both CC BY-SA 3.0 and GFDL compatible.
If a repository contains both code and creative content besides code, then the license file should specify that source code files and code snippets are released under a BSD 3-clause license (that is included in the file) and that all other creative content is released under an appropriate Creative Commons license (which may be linked to from the license file). As an example, LaTeX code will be covered under the BSD 3-clause license, while the document created by compiling that code will be covered under a Creative Commons license.
Licenses that do not allow derivative works or commercial use shall not be used by PlasmaPy except under extraordinary circumstances.
The following is sample language for a repository that contains code and other creative content:
Source code files and code snippets included in this project are licensed under the BSD 3-clause license with an added patent grant. All other content in this project (including content compiled directly from source code and code snippets) is licensed under the Creative Commons Attribution 4.0 International (CC BY 4.0) license.
The following is sample language for a repository that contains code as well as creative content besides code and that allows two-way compatibility with Wikipedia:
Source code files and code snippets included in this project are licensed under a BSD 3-clause license with a patent grant.
Unless otherwise indicated, all other creative content in this work (including content produced directly from unmodified source code and code snippets) is released under the Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0) license. Original contributions (e.g., contributions that are not derived from another work) to this repository may also be shared, adapted, and redistributed under the Creative Commons Attribution-ShareAlike 3.0 Unported (CC BY-SA 3.0) license and/or the GNU Free Documentation License (GFDL).
A copyright notice must be included in every repository. The phrase “All rights reserved” no longer has any legal significance and should not be included.
The Coordinating Committee may adopt different licenses for different repositories when appropriate, as long as the licenses are on the list of OSI approved open source licenses (or at the very least unambiguously meet the definition of open source as described by OSI). Existing open source repositories that are incorporated into PlasmaPy may continue to be licensed under its original license.
Versions of PlasmaPy prior to 2017 October 17 will continue to be available under the original BSD 3-clause license.
- PlasmaPy could use the BSD 3-clause license without the patent grant; however this would remove explicit protections against software patents.
- Another alternative would be to use the Apache License, Version 2.0 which includes specific protections against patents. However, the naming of the Apache license constitutes cultural appropriation which violates the first bullet point in PlasmaPy’s code of conduct on “using welcoming and inclusive language.”
- PlasmaPy software could be licensed under the copyleft GNU General Purpose License 3.0 (GPLv3) or weaker copyleft GNU Lesser General Purpose License 3.0 (LGPLv3). These licenses would require that derivative works be covered by the same license when being redistributed. These restrictions would prevent or restrict use by proprietary packages, but would ensure that derivative works continue to be open. A major disadvantage of these licenses are that they are not two-way compatible with permissive open source licenses, so they would not allow back and forth code sharing with permissively licensed packages. The main disadvantage of not choosing the GPLv3 or LGPLv3 is that code released under those licenses will not be able to be incorporated into a package under a different license.
- Additional alternatives include any of the other open source licenses approved by OSI.
- Alternatives include any of the other Creative Commons licenses or the GFDL.
- The CC0 license would relinquish the copyright of a creative work to the extent allowed by law so that the work is effectively in the public domain. This license would remove the attribution requirement contained within the CC BY and CC BY-SA licenses. However, attribution is beneficial to the scientific process because it allows recipients to better understand the origin of an idea or data which in turn helps reprodicibility.
- Creative Commons licenses that prohibit derivative and/or commercial reuse run contrary to the principles associated with the Free/Libre and Open Source Software (FLOSS) movement.
The BSD+Patent license is permissive and contains clear protections against software patents. This license is two-way compatible with code from Astropy and SunPy. Code under this license or a CC BY license may be relicensed under most other licenses. A CC BY-SA license may be used to allow greater back and forth collaboration with other works under the same license. This policy provides additional flexibility to the Coordinating Committee to deal with extenuating circumstances.