Copyleft

Copyleft is a particular use case of the copyright. It uses copyright to make sure that the people still have the right to distribute, copy and modify [1].

Origin

The concept of copyleft comes from the GNU Manifesto written by Richard Stallman. In this manifesto he asks for help to create his own operating system, GNU, but already states that it won't be in the public domain, but that it will use copyright to allow everyone to distribute, copy and modify it. [2]

Application

Application of the copyleft is based on the Free Software Definition [3]:

• Freedom 0 – the freedom to use the work,
• Freedom 1 – the freedom to study the work,
• Freedom 2 – the freedom to copy and share the work with others,
• Freedom 3 – the freedom to modify the work, and the freedom to distribute modified and therefore derivative works.

Some licences are used to apply the copyleft, such as the GNU General Public Licences. [4]. Creative Commons provides a similar license called ShareAlike.[5].