Your Great-aunt sends you a GEDCOM file of your ancestry on her side of the family. The file includes hundreds of individuals with notes and sources. You immediately decided to publish the information for your family and eventually, you publish a book containing the information from your Great-aunt as well as some of your own work. Did your Great-aunt own any of the information she sent to you? Do you own a copyright in the book you have just published? What parts, if not all, of your work is protected?
The first thing to understand about the current state of copyright law in the U.S. is that "[y]our work is under copyright protection the moment it is created and fixed in a tangible form that it is perceptible either directly or with the aid of a machine or device." Registration is not necessary to obtain protection, and for that matter, it is not even necessary to have a copyright notice on the work. As the U.S. Copyright Office states, "In general, registration is voluntary. Copyright exists from the moment the work is created. You will have to register, however, if you wish to bring a lawsuit for infringement of a U.S. work. See Circular 1, Copyright Basics, section “Copyright Registration.” See U.S. Copyright Office.
So, if any portion of your Great-aunt's work was subject to a copyright, she had those rights when she sent the work to you, even if she didn't claim any copyright protection at the time. Likewise, if any portion of your own publication was your original work, then it too was protected by copyright.
However, you have no copyright protection for the historical information contained in either a computer genealogy file or even a book. Again quoting from the U.S. Copyright Office, "Copyright, a form of intellectual property law, protects original works of authorship including literary, dramatic, musical, and artistic works, such as poetry, novels, movies, songs, computer software, and architecture. Copyright does not protect facts, ideas, systems, or methods of operation, although it may protect the way these things are expressed. See Circular 1, Copyright Basics, section "What Works Are Protected." More specifically, several categories of material are not protected by copyright, including "Works consisting entirely of information that is common
property and containing no original authorship (for example: standard calendars, height and weight charts, tape measures and rulers, and lists or tables taken from public documents or other common sources)." See What Works are Protected.
What if I don't care about copyright? Even if you own the copyright to your work, you do not have to enforce it. You can allow your work to enter the public domain or even notify anyone who cares, that your work is in the public domain.
But if you do care, you need to be consistent and make efforts to protect your copyright. If you find someone has used your material without permission, you must take steps to demand that the material be removed or claim a right to any damages, that is, loss of income you may have suffered as a result of the improper publication or use. Failure to enforce your copyright may end up with your work being in the public domain.
So, the information from your Great-aunt is probably not subject to copyright, like the names, dates, sources etc. but if she wrote any notes about the family, using her own words and expressions, those notes are subject to a copyright claim.
As a final note, for the moment, you cannot take a document that is already in the public domain and somehow make it subject to your copyright. Your index or comments might be protected by you can't prevent people from using the information. Again, to quote the U.S. Copyright Office about works not covered by copyright, they include, "Ideas, procedures, methods, systems, processes, concepts, principles, discoveries, or devices, as distinguished from a description, explanation, or illustration."
More to come.