Authors implementing open practices should remember that whenever a published file or document has no explicit license, it is unclear to potential users what they are allowed to do and what not. Ideally, therefore, researchers should explicitly note the license under which every piece of their published work, including experimental materials, data, and software code, is released.
For material that can be copyrighted, such as materials and code, several open licenses have emerged over the last decades, and their dependencies and (in)compabilities can be quite confusing (for an overview, see Morin, Urban, & Sliz, 2012). Recently, however, some consolidation has taken place based on the work of Creative Commons (CC; http://creativecommons.org/) . The Creative Commons organization provides a simple and coherent system of licenses that focus on openness and have several advantages: they are concise and clear, have both legal and non-expert translations, and the website has a convenient point-and-click license chooser. Furthermore they are optimized to work under the most legislations worldwide.
The CC licenses have been chosen as the standard license for many Open Access journals (e.g., PLOSone, BioMed Central, or the Nature Publishing Group). The default license is the Creative Commons Attribution Licence (CC-BY), which specifies that others are free to copy and redistribute the material in any medium or format, and to remix, transform, and build upon the material for any purpose as long as you give appropriate credit to the original creator, provide a link to the license, and indicate whether changes were made (http://creativecommons.org/licenses/by/4.0/). As variations, the licensor can choose to remove the attribution clause, which would put the work into the public domain (CC0), to add a share-alike clause, which means that every work derived of this work must be open as well (CC-BY-SA), and additionally the license can be restricted to non-commercial use (CC-BY-NC).
The CC-BY license typically is given for the paper itself and Open Material, as long as the material is copyrightable and you are the copyright holder of the material. Licensing of raw data is more complicated, because it cannot be copyrighted. Since version 4.0, however, the CC licenses also contain database rights, and have been implemented as a standard license for Open Data as well (e.g., from the Journal of Research in Personality).
When thinking about what one can, must, or should do with Open Material and Open Data, one has to differentiate on the one hand legally-enforceable rules (which are handled with legal licenses) and, on the other hand, rules and standards of the scientific community. If a piece of work is in the public domain (e.g., a CC0 license) there is no legal requirement to give attribution, but as a scientist one still has the ethical obligation to give a proper citation. Laws, ethics, and professional courtesy are all ways that the community can protect those that open their data.
We recommend assigning an explicit license to every piece of material that is published in a repository. The accompanying website to this paper gives advice on license choices as well as practical recommendations how to add licenses to open data and materials.
- Morin, A., Urban, J., & Sliz, P. (2012, July). A quick guide to software licensing for the scientist-programmer. PLoS Comput Biol, 8 (7).
- Creative Commons: “develops, supports, and stewards legal and technical infrastructure that maximizes digital creativity, sharing, and innovation.”
- British Academy Joint Guidelines on Copyright and Academic Research – Guidelines for researchers and publishers in the Humanities and Social Sciences.