The copyright issue is more complex than "Paley decided to use stuff that was under copyright"; the recordings she used are apparently PD - but the sheet music of these songs has turned out to not be, and is in fact in the hands of several Big Media conglomerates. And by the time this became apparent she was way too deep into the project to abandon it, and just plowed into the Great Work, hoping that it would sort itself out by the time she finished. An attitude I can understand, as an artist obsessive enough to have been in animation!