As an author, you usually transfer certain rights to third parties, e.g. publishers, when you publish your work. Which rights and to what extent depends on the publication medium. Even if you have published in a subscription journal or intend to do so, you can make a version of your publication freely accessible under certain conditions.
If you publish in a traditional subscription journal, you usually transfer the exclusive rights of use to the publisher. When you publish Open Access, you ideally retain all rights and, with open licences, grant rights for subsequent use under certain conditions (see below). Some publishers require the transfer of rights and then publish the article themselves under an open licence.
If you publish in a subscription journal, make sure that you grant the publisher only non-exclusive rights of use if possible. You can then publish your work yourself under an open licence, e.g. in the university repository.
If the publisher insists on the transfer of exclusive usage rights, then negotiate the right to publish the manuscript secondarily in a repository as soon as possible. To amend publishing contracts, there are templates that can be adapted and attached to the contract, e.g. SPARC Author Addendum.
According to Plan S of the cOAlition S, which applies to EU-funded projects among others, all publications must be freely accessible under the CC BY licence without embargo. The cOAlition S has developed a Rights Retention Strategy for this purpose, which ensures that this condition can be met vis-à-vis publishers.
Under no circumstances should you give up Open Access obligations by the funder or the employer, or existing rights arising, for example, from Section 38 of the German Copyright Act or from agreements the library has with publishers, in a contract.
Creative Commons licences are the most widely used open licences. They allow the re-use of a work by third parties under certain conditions. The CC BY (Creative Commons Attribution) licence permits the distribution and use of the work or parts of it on condition that the authors are named and any changes are indicated. CC BY is widely used in science and is the most suitable licence; it restricts subsequent use the least and at the same time ensures that the authors are named. This licence is also recommended in the Leibniz University of Hannover's Open Access Guidelines and is required by many funding bodies.
The short video "Open licenses for open research" explains the use of licenses for scientific works.
Source: Brinken, Helene; Hauss, Jonas; Rücknagel, Jessika: Open licenses for open research, open-access.network. https://doi.org/10.5446/53449
The short video "Creative Commons Licences for Open Access" explains why the CC BY licence is ideal for scientific publications.
Source: Brinken, Helene; Hauss, Jonas; Rücknagel, Jessika: Creative Commons licenses for Open Access, open-access.network. https://doi.org/10.5446/53525