The Impact Of Copyleft On Choosing a Software License

 I assume that most people are familiar with Copyright and how authors can protect their rights by Copyrighting their work. But not a lot of people have heard about Copyleft, the movement that practices the right to freely distribute and modify intellectual property with the requirement that the same rights must be preserved with modified works created from a Copylefted work. The main principles of Copyleft are as follow:

  1. The freedom to use the work
  2. The freedom to study the work
  3. The freedom to copy and share the work with others
  4. The freedom to modify the work and distribute modified works

There are 3 main categories of Copyleft: Strong Copyleft, Weak Copyleft and No Copyleft. Each category of Copyleft also has their own licenses. I am going to talk about all of the different licenses and what advantages and disadvantages each license has.

Strong Copyleft:

Strong copyleft basically means that derived work from another strong Copyleft work has to retain the same license as the original work. Some of the licenses of strong Copyleft are:
  • GNU General Public License - The advantages are that you can copy, modify and distribute the software under this license freely, but the disadvantages are that you cannot change the license of the derived work. This license is the most popular of all the Copyleft licenses.
  • The Affero GPL - The advantage is that with Affero it is necessary to disclose the source code with web applications, which was not the case with GNU GPL and therefore you cannot make proprietary software with Copyleft software in the web that has an Affero license.

Weak Copyleft:

Weak copyleft means that usually the same rules apply as strong Copyleft, meaning that the same licenses have to be retained for derived works, there are some exceptions to this rule like software libraries where the license does not have to stay the same for derived works. Some of the licenses of weak Copyleft are:
  • GNU Lesser GPL - This license is mostly used for software libraries and it's advantages are that you may copy, modify and distribute the software, but the disadvantage is that you have to clearly describe the modifications and license them for free.
  • Mozilla Public License - MPL is a very easy license to comply with. You have to make the source code available and you can even combine the MPL code with proprietary code, but you have to store them in separate files.
  • Microsoft Reciprocal License - The disadvantages of MRL is that you have to give access to users so that they may view, modify and distribute the software.
  • The European Union Public License - The first open source license to be released by an international governing body and the objective of this license is to create a license available in every language of the European Union.

Non-Copyleft or Permissive Licenses:

The no Copyleft licenses can be derived to make proprietary applications and this gives the developers the most freedom, but this also means that end users cannot be sure if the derived software will be free to use or not. Some of the licenses of Non-Copyleft are:
  • BSD License - The advantages of BSD are that it does not require for the source code to be distributed. That means less work for the developers to constantly document their work for anyone that is unfamiliar with the software.
  • Apache License - The advantages of the Apache license is that they do not require the distribution of the software under the same license, but all of the parts that are unmodified still have to be under the same license.
  • MIT License - The MIT license permits the reuse of licensed software within proprietary software, but all software that has used MIT licensed code has to have a notice or a copy of the MIT License terms included in the software.

References:

  • https://www.gnu.org/licenses/copyleft.html
  • https://copyleft.org/
  • https://snyk.io/learn/what-is-copyleft-license/
  • https://opensource.com/resources/what-is-copyleft
  • https://www.britannica.com/topic/copyleft
  • http://www.ipdigit.eu/2015/09/the-scope-of-copyleft-effect-whats-right-and-whats-left-part-ii-triggering-copyleft/
  • https://firstmonday.org/ojs/index.php/fm/article/view/1368/1287
  • https://tldrlegal.com/licenses/tags/Copyleft
  • https://wiki.p2pfoundation.net/Copyleft
  • https://en.wikipedia.org/wiki/Copyleft

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