Open Source Licensing
In the U.S., copyright owners have exclusive rights to their works including the right to use, copy, modify, and distribute the copyrighted work. The Copyright Act extends these rights and protections to software source code and software creators may choose to then license their rights to users of the software. In choosing to license their software, creators retain their rights in the work but grant permission to others to use the work under certain terms and conditions.
Under traditional proprietary licenses, software creators can limit how others use their copyrighted software by means of end user license agreements that prohibit copying, modifying, or redistributing the software. The copyright to the software is further protected by only providing the user with the object code for the software which cannot be easily read or modified.
Alternatively, software owners can choose to make the source code available to users and allow them to freely use, copy, modify, and redistribute the software under open-source licenses. An open-source license thus gives the user both the ability and legal right to modify the software. However, software provided under an open-source license is still subject to copyright protection and failure to comply with the license terms can be grounds for legal claims of copyright infringement as well as breach of contract.
There are hundreds of open-source licenses and variants which generally fall under two broad categories: restrictive or permissive. Under both types of licenses, users are allowed to use, modify, and redistribute software but the licenses differ in how subsequent modifications, derivatives, or new programs are licensed. Under a restrictive license, also known as copyleft or reciprocal license, the derivative work must be licensed under the same open-source license as the original software meaning it must be offered to others to use, modify, and redistribute under the same terms. Conversely a permissive license allows derivative works to be licensed under a proprietary license.
Some of the most popular open-source licenses include:
MIT License https://opensource.org/licenses/MIT
- Permissive
- License to use, copy, modify, and distribute software
- May distribute under different licenses and without source code
- Must include copyright notice and license agreement
GNU General Public License (GPL) v3.0 https://www.gnu.org/licenses/gpl-3.0.html
- Restrictive
- License to use, copy, modify, and distribute software
- Commercial, private, and patent use
- Must disclose source and include license and copyright notice
- Must make complete source code of licensed works and modifications available
- Must distribute under same open-source license
Apache License v.2.0 https://www.apache.org/licenses/LICENSE-2.0
- Permissive
- License to use, copy, modify, and distribute software
- Commercial, private, and patent use
- May distribute under different licenses and without source code
- Must include license and copyright notice
Creative Commons (CC) 3.0 https://creativecommons.org/licenses/by-nc/3.0/legalcode
- Restrictive
- Must attribute author as creator
- Non-commercial use
- License to copy and distribute
- No derivatives
