Notes on Copyright
This document should hopefully provide help with copyright law and the use of our Project Gutenberg corpus. The Summary should provide all the necessary information for 99.9% of cases, but some edge cases are explicated under "Finer points."
Let me know if you have any further questions!
—Derek Yen, Copyright and License Specialist, Data Group
Books which are in the Public Domain are not subject to copyright. We can use books in the Public Domain without requesting special permissions.
Any book first published before 1923 is in the Public Domain in the United States.
As we are working in the United States, we operate entirely within US copyright law. The above "published before 1923" rule is our biggest consideration.
Project Gutenberg is based in the United States, so the bulk of their book uploads are in the Public Domain in the United States.
See below for the exceptions to the above.
U.S. Copyright Law
Because any book first published before 1923 is in the Public Domain, any book which is still copyrighted cannot have been published before 1923. Because our study only examines books written from 1770-1922, any book that is still copyrighted is not within our time period of interest and not the subject of this study. However, do note the following:
Not all books in the Public Domain were first published between 1770-1922. Books can enter the Public Domain other ways, eg if a book's author voluntarily enters it to the Public Domain. There are books in the Public Domain which are not the subject of our study.
Additionally, pay attention to the exact book you are downloading. Some books may appear to be books which are within the public domain, but are not. For example, a publication of one of Shakespeare's plays (all in the public domain) could be itself not in the public domain if it contains copyrighted content, such as scholarly essays or annotations. This should not be relevant because scholarly annotations, essays, forewords, etc. are not themselves literature and should not be processed anyway, but this is an additional reason to ensure that scraped books are actually just books.
Project Gutenberg is based in the US, so the majority of their uploads are in the Public Domain in the US. There are some exceptions.
Some works uploaded to Project Gutenberg are under copyright, but have been uploaded with permission. However, any book copyrighted cannot have been published before 1923, and is thereby outside the scope of our study anyway. Do not use works that are still copyrighted.
Project Gutenberg does not provide the first publication date of works they've uploaded; this information must be obtained elsewhere. There are some books in the public domain that were not first published before 1923, so do not use a book's copyright status to assume that it is within our search period.
Project Gutenberg provides info about the copyright status of works they've uploaded, which can be viewed under "Bibrec." See below: