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Public and Open licenses

Public Licenses

How is a CC license different from my contract with the editor? (Public vs. bespoke licenses)

A license can be an agreement (a contract) between the licensor and the licensee including any freely negotiated terms. Such a license is sometimes referred to as a ‘bespoke’ license, or a custom-made license. In order to simplify the licensing process, avoid interoperability problems and achieve some common goals, standard ‘public’ licenses started to appear in the 1980s.

A public license allows the licensor to authorise the general public (i.e. everybody) to perform certain uses of his/her work; if such a license is used, it is no longer necessary to grant individual permissions (and e.g. answer dozens of requests per day). From the legal point of view, a public license is an offer to conclude a contract; this offer is then accepted by conduct when a user starts using the licensed work. Therefore, public licenses are still binding contracts which should be respected. When it comes to licensing of research data, public licenses should be used whenever possible.


Public Licenses for Data and Software

There is a relatively wide range of readily-available public licenses for software as well as for other works.

Non-software licenses (Data licenses)

The most popular public licenses used for data are the Creative Commons (CC) ones.

Creative Commons is a non-profit organisation founded in 2001 by - among others - Lawrence ‘Larry’ Lessig, a law professor at Harvard Law School. The organisation proposes a suite of public licenses known under the same name. Their most current version (4.0) was released in November 2014 and is a major improvement, as it covers not only copyright, but also related rights, such as the sui generis database right, which makes it a perfect tool for licensing of research data.

Previous versions of CC licenses may exist in national (ported) versions, i.e. versions that are not only translated, but also adapted to national jurisdictions. In our view, the use of ported versions of CC licenses should be avoided, due to compatibility problems.

Creative Commons licenses are built of four building blocks, each corresponding to a different requirement.

  • BY (attribution): this is a mandatory element of every CC license. Contrary to what is commonly believed, the attribution obligation in CC licenses extends beyond a simple indication of the name of the author; in fact, the user is obliged to retain a copyright notice (e.g. "(c) 2016 Paweł Kamocki"), a license notice (e.g. "This work is licensed under a Creative Commons Attribution 4.0 International License"), a disclaimer of warranties (if supplied) and a link to the licensed material.
  • SA (share-alike): according to this requirement, if derivative works are made, they have to be licensed under the same or compatible license, i.e. a license containing the same (or compatible) requirements. There is only one license approved for compatibility with CC BY-SA 4.0 license: the Free Art License 1.3. In every other case, in order to comply with the SA requirement, you will have to re-license the derivative work under the same CC license, or its more recent version.
  • NC (non-commercial) means that no commercial use can be made. Commercial use is defined as use primarily intended for commercial advantage or monetary compensation. Please note that this category is extremely unclear and can discourage potential users. In our view, when it comes to licensing of research data, this requirement should be avoided.
  • ND (no derivatives) means that no derivative works can be made, i.e. the material cannot be modified, adapted or translated, but can only be used "as is". Arguably, adding another layer of annotation or meta-data, or even incorporating the material into a larger dataset would violate this requirement. Therefore, licenses containing the ND requirement should not be used for research data.

These four building blocks can be combined into six different licenses:

Please note that the BY requirement is a mandatory element of every CC license, and that SA and ND requirements are mutually exclusive. Only CC BY and CC BY-SA meet the standards of the Open Definition, and only CC BY is compatible with Open Access standards (see What is an ‘open’ license? below).

Apart from the licenses, Creative Commons offers also other tools. These include:

  • CC0 ( a copyright waiver, i.e. a tool by which the rightsholder assumes an obligation not to exercise his/her exclusive rights. In theory, CC0 material can be used without any restrictions at all; however, in our view the tool raises some doubts as to its enforceability in many EU jurisdictions. Before you decide to use it, consult the legal department in your institution.
  • CC+ (CC Plus): a rather obscure tool that allows the rightsholder to add a requirement to one of the CC licenses to ‘open it up’. For example, by adding a ‘plus’ to CC BY-NC, the licensor can allow certain commercial uses of his work under specific conditions (e.g. for a fee, or free of charge for small companies). The ‘plus’ clause should be drafted by a professional lawyer. For more information see:
  • Public Domain Mark ( can be applied to a work that has been identified to be free of copyright. This is only an information sign and does not waive any rights or create any obligations. You can use it e.g. if you are sure that copyright in the work expired, e.g. because the author died more than 70 years ago; that can save others some time.

Please note that CC licenses are not appropriate for software licensing. For software licenses, see below.


Software Licenses

There is a plethora of available software licenses which can be divided into three categories:

  • Permissive licenses contain only minimal conditions concerning the use, modification and re-distribution of software. This means that there is no guarantee that modified versions of the software will remain ‘open source’, or free. The most popular of those licenses are BSD, MIT and Apache licenses.
  • Strong copyleft licenses contain an obligation to license modified versions of software under a compatible license (cf. the SA requirement in CC licenses), therefore preserving its ‘openness’. The most common license of this kind is the GNU GPL (General Public License) in its various versions.
  • Weak copyleft licenses are used to license software libraries; the copyleft requirement in these licenses applies only to the modifications of the code, and not all the code that is linked to it. These licenses allow linking between software licensed under copyleft and permissive licenses. The most common examples of such a license are GNU LGPL (Lesser GPL) and Mozilla Public License.


Multi-licensing and re-licensing

Public licenses are in principle irrevocable. However, it is possible to re-license material under a different license, or even to license it under several licenses from the start (this practice is called multi-licensing). If material is licensed under several licenses, these licenses do not apply cumulatively, but alternatively, i.e. the user can choose under which license he/she wants to use the material (logically, he/she would choose the least restrictive license, or the license which is compatible with his/her project). Multi-licensing can not only ‘open up’ material that is already licensed (e.g. material licensed under CC BY-NC can be re-licensed under CC BY), but also solve some specific interoperability problems (e.g. software can be licensed under two incompatible licenses, like GPL and Artistic License, in order to de facto increase its reusability).


Open Licenses

What is an ‘open’ license?

Open Science is the movement to make scientific research, data and dissemination accessible to all levels of an inquiring society ( Open Science revolutionizes the knowledge discovery process by amplifying collective intelligence and bringing people with various microexpertise together.

For more information about Open Science in general, see:

The Open Science movement is based on several principles, most of which have been developed before the term Open Science was introduced [see:]. Some of these principles refer to organisational aspects of scientific work (Open Methodology, Open Peer Review); others, however, are directly connected to IP licensing. The latter include: Open Access, Open Data and Open Source. Please note that each of these standards adopts a slightly different definition of openness.

Open Access

The Open Access (OA) movement concerns access to scientific literature, e.g. academic journal articles, conference papers, theses, book chapters, and monographs (but not research data).  It was initiated by three declarations (often jointly referred to as 3B): the Budapest Open Access Initiative (2002), the Bethesda Statement on Open Access Publishing (2003), and the Berlin Declaration on Open Access to Knowledge in the Sciences and Humanities (2003).

Two approaches to OA can be distinguished: gratis OA and libre OA (see: P. Suber, Gratis and Libre Open Access, available at: Gratis OA simply means free online accessibility, but says nothing about any re-use rights: a scientific paper is gratis OA, if it can be accessed for free (without subscription fees) on the Internet, but not further re-used (eg. analysed with a piece of software or modified in any way). Gratis OA does not require any specific licensing solutions (an ‘all rights reserved’ paper can still be freely accessible on the Internet). By contrast, Libre OA consists in granting the user some re-use rights. Unfortunately, there seems to be no common definition of Libre OA, as each of the 3B declarations adopts a slightly different approach. It seems, however, that according to all of them a very broad range of re-use rights should be given to the user (the texts mention the rights to: read, download, copy, distribute, print, search, link, crawl for indexing, pass as data to software, transmit, display publicly, make and distribute any derivative works) which can be exercised for any (‘lawful’ or ‘responsible’) purpose, including commercial uses. The only condition is proper attribution of authorship. In terms of licensing, it seems that Libre OA is therefore best achieved via the use of a CC BY license (preferably 4.0).

There are essentially two ways to publish an OA paper, referred to as green and gold OA [for more information, see here. Green OA refers to self-archiving (e.g. in an institutional repository or even on a personal website); gold OA refers to publishing in an open-access journal (a situation in which the author has no publication fee to pay has recently been referred to as diamond OA).

Under article 29.2 of the Horizon2020 Model Grant Agreement, each beneficiary must ensure open access to all peer-reviewed scientific publications relating to its results (for more information see here).


Open (Research/Science) Data

The concept of open data for science predates the Internet (a landmark date is 1958, the year in which the World Data Centre, now transformed into the World Data System, was created), but it is in the Digital Age that the movement gained momentum. The most commonly used definition of Open Data is the so-called “Open Definition” proposed by Open Knowledge International. According to its short version, a dataset is open if  "anyone can freely access, use, modify, and share for any purpose" (subject, at most, to requirements that preserve provenance and openness).” (see full version).

In this approach, openness of datasets is best achieved through the use of CC BY 4.0 and CC BY-SA 4.0. Other less popular licenses: ODC-BY and ODbL (roughly equivalent to CC BY 4.0 and CC BY-SA 4.0), as well as waivers (CC0 and its equivalent PDDL) can also be used. The use of GNU FDL (Free Documentation License) is not encouraged as this license is not compatible with any other license. For more information regarding licenses that comply with the Open Definition, see:

Please note that datasets may often contain personal data (see Personal Data protection), in which case they are difficult to be made publicly available.

OpenAIRE’s Open Data Pilot addresses the issue of ‘open access to research data’ [sic] generated by selected Horizon 2020 projects.

Apart from researchers, governments and public institutions are an important source of open data. Typically, public bodies release their data under a country-specific license, e.g. DatenLizenz Deutschland in Germany, Open Government License in the UK, Licence Ouverte in France. It is our view that the use of such licenses in research should if possible be avoided.


Open Source, or FOSS (Free Open Source Software)

Chronologically, Free Software/Open Source is the first ‘open’ movement and a source of inspiration for other such initiatives. It started in mid-1980s, when Richard Stallman, an MIT-educated hacker, announced the GNU project (aiming at creating an open-source operating system) and when the Free Software Foundation (FSF) was founded. The GNU project eventually led to the creation of Linux in early 1990s. Subsequently, the movement drew more attention from the software industry (e.g. the source code of Netscape Internet suite was released, which enabled the creation of Mozilla Firefox). In order to make open-source model more appealing to business, the Open Source Initiative (OSI) was founded, promoting a somewhat more lenient and business-friendly conception of Open Source Software.

According to the Free Software Definition (originally published by Stallman in 1986), software is free when four freedoms are given to its every user:

  • Freedom 0: The freedom to run the program as he wishes, for any purpose.
  • Freedom 1: The freedom to study how the program works, and to change it. This freedom requires access to the source code.
  • Freedom 2:  The freedom to redistribute copies.
  • Freedom 3: The freedom to distribute copies of modified versions, i.e. to give the whole community a chance to benefit from the changes.


The Free Software movement emphasises the user’s freedoms and often refers to such ideological concepts as freedom and fairness. It is primarily associated with GNU GPL, a copyleft license, and its various derivatives (LGPL, Affero GPL), but it also approves many other licenses (see:

The Open Source Initiative (OSI) maintains a list of approved licenses which comply with the Open Source Definition. Among these, the licenses that are widely used and that have strong communities are particularly recommended [see:]. The latter include:

  • Apache License, 2.0 (Apache-2.0)
  • BSD 3-Clause "New" or "Revised" license (BSD-3-Clause)
  • BSD 2-Clause "Simplified" or "FreeBSD" license (BSD-2-Clause)
  • GNU General Public License (GPL)
  • GNU Library or "Lesser" General Public License (LGPL)
  • MIT license (MIT)
  • Mozilla Public License 2.0 (MPL-2.0)
  • Common Development and Distribution License (CDDL-1.0)
  • Eclipse Public License (EPL-1.0)

 As a matter of fact, although the Free Software movement and the Open Source movement are based on different premises, most licenses approved by the FSF are also approved by the OSI (the exceptions are few and rather insignificant; see a chart at: A license that complies with both standards (including all the licenses mentioned above) are sometimes referred to as FOSS (Free Open Source Software) licenses.

Please note that ‘open source’ refers to the freedom of use, modification and redistribution, rather than absence of fees. It is therefore (theoretically) possible that open source software is not ‘free’, and that free software (freeware) is not open source, even though in practice these two categories will often overlap.