Copyright is a monopoly granted by the government. It gives the author control over reproductions, translations, adaptations, performances, communications, etc. of their work for a fixed time. Since 1978, it has not been necessary to register a copyright—it is automatic. So for example, every web page, no matter how simple or unrefined, is copyrighted by its author.
The phrase “All Rights Reserved” is used to assert that the copyright holder intends to exercise all the rights granted by copyright. It is not required to mark a document with the copyright symbol (©) but in case of disputes, it can be helpful.
So in PreTeXt you can go
<frontmatter> <colophon> <copyright> <holder>Thomas Jefferson</holder> <year>1776</year> <minilicense>All Rights Reserved</minilicense> </copyright> </colophon> </frontmatter>
to assert a “traditional” copyright and the recommended information will then appear on the page after the title page.
In academic publishing, authors have usually transferred, or sold, their copyright to a publisher in return for distribution of their work, or for the promise of financial gain.