Attributing works in the public domain
Works might be in the public domain typically for any of the following reasons:1
- because copyright has expired;
- because it was never entitled to copyright to begin with;
- because the rights over the work have been waived.2
Copyright only lasts for a certain amount of years (typically, 70 years after the death of the author, although some countries only require 50 years post mortem and some other countries require more). When a work is in the public domain, typically that means that it’s free to use. However, some jurisdictions have a different approach, particularly those that strongly protect moral rights, requiring that the user of such a work still attributes the original author.
Since depending on the jurisdiction in which you are based the situation might vary, you might need to attribute the work even when the work is in the public domain. Additionally, a good idea is to follow what is suggested in the Public Domain Usage Guidelines prepared by Europeana, the aggregator of cultural heritage in Europe.
In certain cases, authors might choose to waive all their rights, and make it optional to attribute them or not. That’s the case of the authors that choose the CC0 tool (“Creative Commons Zero”), a public domain dedication that puts the work in the public domain once the author has decided to apply the tool. In this case, you can decide whether you attribute the work or not.
1 Additionally in the US works might be in the public domain due to failure of registration prior to the granting of automatic protection, but that situation is very specific and won’t be explored here.
2 This is the case not only for authors using CC0 but also for certain types of work, such as works made by US officials in the context of their employment. However, that rule only applies under US jurisdiction, so make your own risk assessment to whether use or not any of those resources.