SPEAIT2021K: Copyleft

”Copyleft is a method for making a software program free, while requiring that all modified and extended versions of the program also be free, and released under the same terms and conditions. When an open source software project is published with a copyleft license, other developers have the right to use, modify, and share the work as long as the reciprocity obligation is maintained.” - Goldstein, Whitesource, 2019

Copyleft logo

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Even thought the copyleft is and sounds pretty free concept it has its own strict rules too and for that there is created several of versions and concepts of the Copyleft. Some of the licenses are more permissive than the others. The Copyleft can be classically divided in to four categories; strong and weak ones and also full and part-licenses too. The strong copyright as it's name already says is strong and requires strict license following, where the weak one is not so strict and the user is able to link it to the other licenses for example. What comes to the full and part-licenses, they describe does the particular license affect to the whole software or only to part of it.

In practical copyleft-licenses gives more freedom to create, distribute and develop the software or product, not alone but with the help of others. Gives more freedom for the user and a possibility to change it the way he likes it to view and use. The usefulness of open source is not based only on the exploitation of open source but on reciprocal interaction with open source communities.

A software licence defines what users are allowed to do with the software, possible restrictions to the use, obligations and responsibilities. The aim of the lisence is to protect both developers and users — it gives the license specific rights and it may also include limitations of liability, warranties and warranty disclaimers. Software that is published without a license is legally unusable, because no usage rights are granted by a license. Therefore, it is extremely important to define a license for a software if the software is distributed and not for internal or private use only.

The selection of the right copyleft license depends most of all the purpose of the software, impact and what it’s used for. In many of my sources there was pointed out that it is very important to understand the main differences between different licenses instead of just picking a random license that sounds good. The first step is to understand different license types, and choose a license type that best fits to the needs of the software project and it’s purpose.

"If you ask most developers, they’ll say they want a copyleft, because they want to avoid their work being co-opted or exploited (or even “hijacked”)." - Cartwright, Free Software Magazine, 2008

List of different copylefts and example of them:

Licenses with strong copyleft

The GNU General Public License - WordPress, Wikipedia
The Affero GPL (the extra strong) - Peertube (a free and open-source video platformthat uses peer-to-peer technology to reduce load on individual servers when viewing videos.)

Licenses with weak copyleft

The GNU Lesser General Public License -
VLC media player (a free and open-source, portable, cross-platform media player software, and streaming media server)
The Mozilla Public License - Mozilla Firefox (free and open-source web browser)
The European Union Public License - created on the initiative of and approved by the European Commission in 22 official languages of the European Union.
Microsoft Public License and Reciprocal Public License -

Non-copyleft (permissive) licenses

The BSD license - Django (high-level Python Web framework that is a set of components that provide a standard way to develop websites fast and easily.)
The Apache license - IntelliJ IDEA (
integrated development environment (IDE) written in Java for developing computer software
)
The MIT (X11) license - Ruby on Rails (server-side web application framework written in Ruby)

Creative Commons, online content licenses

(Created more for pictures, videos and articles etc, softwares that uses some of the Creative Commons license are Youtube, Flickr and DeviantART) Those Creative Commons licenses can be divided into next categories: