Open Content licences are used to ensure the use of publications beyond the limits set by copyright law and thus enable a wider distribution of scientific literature. These licences are free, internationally recognised, standardised contracts that enable the unrestricted use of copyright-protected works. However, the use of Open Content licences is only possible if the authors have not granted exclusive rights of use to a publisher. Further information can be found on the page Open Access paths of publication.

The licences of the Creative Commons series are particularly popular in the scientific field. Less common, but also frequently used, are the Digital Peer Publishing licences (only for digital documents) and the GNU Free Documentation licences (limited to the Anglo-American legal area). However, not all open content licences offered are the same. Some, for example, place greater restrictions on the use of works and cannot be described as open access in the strict sense. To better understand these differences, it is worth taking a closer look at the various licences that are part of the Creative Commons series.

With a Creative Commons (CC) licence, authors can easily grant rights of use for their works to the public without affecting the copyright protection of the work. A detailed explanation of the CC licence agreements can be found on the Creative Commons website.

CC licences are currently available in version 4.0 International and come in seven variants. Starting with those that give the most rights of use, they can be briefly described as follows:

• CC0 1.0 Universal: it differs from all other CC licences because it is used to renounce copyright protection and therefore places the work in the public domain. However, as no full waiver of copyright is permitted in Germany, the use of this licence can be restricted.

• CC BY (Attribution 4.0 International): this licence allows users to distribute, edit, modify and build upon a work, for commercial or non-commercial purposes, as long as they give proper credit to the original author. This licence grants most rights of use without waiving copyright protection. It is therefore compatible with any definition of Open Access and is recommended by the HTW in its Open Access Policy.
• CC BY SA (Attribution-Share Alike 4.0 International): this licence allows users to distribute, edit, modify and build upon a work, for commercial or non-commercial purposes, as long as they properly acknowledge the original author(s) and the new creation based on the original work is published under the same conditions.
• CC BY ND (Attribution-NoDerivatives 4.0 International): this licence allows users to redistribute the work for commercial and non-commercial purposes, as long as this is done without modification, in its entirety and the author is acknowledged.
• CC BY NC (Attribution-NonCommercial 4.0 International): this licence allows users to distribute, edit, modify and build upon a work, as long as they give proper credit to the original author. Commercial use without express permission is not possible.
• CC BY NC SA (Attribution-NonCommercial-ShareAlike 4.0 International):  this licence allows users to distribute, edit, modify and build upon a work, as long as they properly acknowledge the original author(s) and the new creation based on the original work is published under the same conditions. Commercial use without express permission is not possible.
• CC BY NC ND (Attribution-NonCommercial-NoDerivatives 4.0 International): this licence allows users to redistribute the work, as long as this is done without modification, in its entirety and the author is acknowledged. Commercial use without express permission is not possible.

As this description shows, only CC BY and CC BY-SA licences are therefore compatible with the requirements of the "Berlin Declaration on Open Access to Knowledge in the Sciences and Humanities" (of which HTW Berlin is a signatory). In order to truly qualify as open access, the licences must permit any kind of revision and use for any responsible purpose (including commercial use).

Therefore, licences with the NC component for the exclusion of commercial use (often difficult to define) and the ND component for the exclusion of adaptations are generally considered incompatible with the principles of Open Access and are therefore not recommended. The use of these licences can also lead to exclusion from the funding process for Open Access publications (see also the Funding webpage).

If there is a tangible risk of the commercial sale of works by third parties and you wish to protect your creation from such use, the only valid alternative to the CC BY licence is the CC BY SA licence. That is because this licence requires that adaptations of the original work or new works based on it or parts of it may only be distributed under the same licence that was used for the primary creation, which essentially excludes any use for the purpose of commercial distribution.