Relicensing from second parties to third parties is acceptable, because so long as my publication is discoverable (via catalog, search engine, etc...), the third party could obtain the public-domain work that I had originally published.
Somewhat analogously, in the United States you can publish copyrighted works that contain, and even largely consist of, public-domain content. An example off the top of my head is this book [ CliffsComplete Shakespeare's Hamlet ]( https://www.amazon.com/CliffsComplete-Shakespeares-Hamlet-Wi... ) that I used in school. This was how I was introduced to, and first read, the play. The bulk of the text consists of Shakespeare's "Hamlet", which is in the public domain in the United States, and does not require attribution or licensing. The annotations, footnotes, and explanations are original and copyrighted by the publisher (Cliff's Notes). However, I can extract the original play within and redistribute it, or novel works based on it, without worrying about violating rights held by Cliff's Notes.
Somewhat analogously, in the United States you can publish copyrighted works that contain, and even largely consist of, public-domain content. An example off the top of my head is this book [ CliffsComplete Shakespeare's Hamlet ]( https://www.amazon.com/CliffsComplete-Shakespeares-Hamlet-Wi... ) that I used in school. This was how I was introduced to, and first read, the play. The bulk of the text consists of Shakespeare's "Hamlet", which is in the public domain in the United States, and does not require attribution or licensing. The annotations, footnotes, and explanations are original and copyrighted by the publisher (Cliff's Notes). However, I can extract the original play within and redistribute it, or novel works based on it, without worrying about violating rights held by Cliff's Notes.