Meaning: Appropriate authorship and rights information must be provided. This means that the author or authors, the source, and the licence (including reference/link) of the work must be given. It must also be stated whether and, if so, how changes have been made.

Consequence and problem: Attribution is mandatory. Each of the licences requires appropriate authorship and rights statements when the licensed work is used. This may lead to complicated authorship and rights statements in the case of multiple derivative works.

Note: With CC0, Creative Commons also offers the option of waiving the condition of attribution. This is appropriate for marking works for which no copyright protection is possible or given from the outset, and for works that one would like to release into the public domain. This can be useful for certain types of research data, among others. You can find more on this in the frequently asked questions (below).

Meaning: Modifications are permitted but only under the restriction that the modified works are licensed under the same licence as that of the original work when published.

Consequence and problem: In practice, the condition Share Alike has the effect of the licence being inherited. For adapted works, it is therefore effectively contagious in the event of publication—with no remedy. This is precisely the problem: If parts of a work licensed in this way are to be used in a new work (e.g., an illustration or a research article that is to be reprinted in an anthology), this new work would have to be published with the same licence. At first glance, this seems positive because it ensures that free content is created once again. In practice, however, this is often not possible, for example, because the new work is supposed to be published with a more open licence, because it is not published open access and thus without an open licence, or because different works are supposed to be reused whose licences are incompatible to one another.

Meaning: Modifications or a remix of the work are not permitted to be distributed or published.

Consequence and problem: The exclusion of modifications is absolute. Only unmodified use is then possible. This makes many legitimate and, above all, very common cases of reuse impossible, for example, the use of an illustration or a longer section of text in a new work. The Creative Commons licences do not offer the possibility of allowing or prohibiting only certain modifications.

Meaning: The work is not permitted to be used for commercial purposes.

Consequence and problem: The exclusion of commercial use is often favoured in science at first glance. However, what constitutes commercial use is often misunderstood and consequently also how extensive this exclusion is. A use is considered commercial if it is primarily geared toward remuneration or a monetary benefit (commercial is not synonymous with the earning of profits). Moreover, commercial uses are quite common both in science and in education in general: Scientific publishing and scientific events can often be considered commercial; private universities and scientific institutions operate commercially; and in education, nonprofit organisations, associations, small- and medium-sized enterprises, freelancers, self-employed persons, and other actors clearly operate in a commercial field. All of these sectors and actors would be categorically excluded from using works with licences that prohibit commercial use. Additionally, the lack of clarity and legal uncertainty in the interpretation of commercial and noncommercial use leads to the situation that the use of works is also refrained from as a precautionary measure because the noncommercial purpose is too ambiguous or not guaranteed or the expertise for a proper assessment is not available.