Licences play a pivotal role in enhancing transparency regarding the ways in which copyright-protected materials can be used, fostering clarity and facilitating lawful and collaborative sharing. To enable others to use your copyright-protected material, it's essential to establish clear conditions of use, often through the use of a licensing framework. Without a licence, copyrighted protected material may only be utilised with the explicit permission of the copyright holder. In the fields of biodiversity and environmental science, interdisciplinary collaboration plays a central role, resulting in a multitude of creators or contributors. It's important to ensure the active participation of all creators when licensing copyright protected materials. In case of any uncertainties, do not hesitate to seek guidance from your institution's designated point of contact. In the following, their are some recommendations based on common, internationally approved licences for various data types:

Creative content
Creative Commons licences provide a flexible framework for sharing and using creative work (e.g. text, articles, images, figures; see Figure). Just as the European Commission in its project Horizon 2020, the DFG recommends the use of these licence types. When deciding on a specific licence, the guiding principle is “as open as possible, as restrictive as necessary”. The CC0 licence offers complete freedom, allowing users to use the work without any restrictions, often referred to as "No rights reserved." On the other hand, CC BY permits free use but requires attribution to the original creator, ensuring proper credit for their work. These licences enable a balance between openness and recognition in the sharing of creative content.

The use of further licence modules is not recommended. For example, the Creative Commons (CC) licences with the attribute “ND” (e.g. CC-BY-ND) rule out the distribution of “modified” material. This would make it impossible to make a new database publicly available that was created from parts of other databases [1] [2]. The use of a “NC” licence may seem attractive, because many want to prevent commercial exploitation of their research data. However, the term “commercial” is defined in a very broad sense in the CC licences, resulting in major legal uncertainties about which uses are allowed and which are prohibited. For example, if you are exclusively employed by an exclusively publicly funded institution (third-party funding, even from public sources, is already a grey area), you may use CC BY-NC licensed material. However, if you want to publish research that is based on or involves CC-BY-NC licensed material, you cannot publish in any commercial journal (all publishers are commercial, even if they are not-for-profit). Even publishing that research in a private blog that e.g. uses GoogleAds to cover server costs is prohibited. Even any increase in reputation may be considered commercial - and reputation is a major factor in scientific careers. For details, see [3][4]. 

Figure 7.  Creative Commons License Spectrum by Shaddim, CC BY 4.0

Database material
Database material generally refers to the data and content stored within a database. This can include a wide range of information, such as text, numbers, images, audio files, or any other type of structured or unstructured data from different sources that is organised and stored within a database system. Open Data Commons licences offer an alternative framework for sharing database material. The Public Domain Dedication & License (ODC-PDDL) is similar to CC0, granting complete freedom to use data without any restrictions, essentially declaring it "No rights reserved." For those seeking attribution, the Attribution Licence (ODC-BY) allows free use but requires acknowledgment of the data source. An additional recommendation by the DFG (German Research Foundation) is the use of CC BY 4.0, aligning with the international CC BY framework, which encourages open data sharing with proper attribution. These licences serve to promote transparency and accessibility in data sharing while accommodating different preferences for attribution.

Software 
Software, unlike much other research data, require separate licences that are specifically designed for sharing software. The use of Creative Commons licences is not recommended for this. Various open-source licenses offer different terms for sharing and using software. The General Public License (GNU GPLv3) allows free use while mandating that any reusing or publishing must occur under the same license. It also requires the indication of changes made to the code. The Massachusetts Institute of Technology License (MIT) permits free use, but attribution is necessary. The Mozilla Public License (MPL) goes a step further, necessitating the disclosure of changes to the source code and sharing of a narrower set of code under the same license, with all three licenses emphasizing transparency and proper credit in software sharing.

Raw data and metadata
These data are not typically protected by copyright. By using tools like CC0 and the Public Domain Mark, you not only release these resources for unrestricted use but also underscore the absence of copyright restrictions. This practice serves to emphasise and promote transparency, facilitating the exchange and collaborative use of data and metadata among researchers and the wider community. CC0 is a legal tool that allows creators to waive all copyright and related rights in a work, essentially granting it to the public domain. This means anyone can use the work for any purpose without restrictions. On the other hand, the Public Domain Mark signifies that a work is already in the public domain and free from copyright. While both CC0 and the Public Domain Mark serve the purpose of promoting open access to creative works, CC0 is a proactive choice by creators, whereas the Public Domain Mark is applied to works that have already entered the public domain.

In a scientific context, the combination of data from different sources is a common and important part of research. Making data interoperable is supposed to facilitate re-use and re-combination. However, not all CC licences are compatible (Figure 8). Therefore, it is important to choose an open licence like CC0 or CC BY 4.0.

Figure 8. CC licence compatibility chart by Kennisland, CC0.