Who would own derivative works made while it was in public domain?
I create a derivative work (compilation of my favorite chapters from X PD books, including much new commentary from me). The copyrights to that belong to me (in US at least). Then all of the sudden those X PD books are now copyright by X new/previous holders.
What a cluster fuck. Make bunch of lawyers rich arguing over it though.
That's part of the case, if I understand it: some of the plaintiffs are publishers who published sheet music that was at the time in the public domain, but was then re-copyrighted, forcing them to pull those publications.
What unfortunately doesn't seem to be part of the case, but would make for an even stronger plaintiff (at least rhetorically), would be an orchestra that recorded a public-domain work but then found itself unable to distribute its own recording, once it was re-encumbered.
I create a derivative work (compilation of my favorite chapters from X PD books, including much new commentary from me). The copyrights to that belong to me (in US at least). Then all of the sudden those X PD books are now copyright by X new/previous holders.
What a cluster fuck. Make bunch of lawyers rich arguing over it though.