OK. I get that. So Mr Worts based PHANTOM PRESIDENT on the public domain PRISONER OF ZENDA. One can accept that. But Mr Worts moved the story forward, and now its a President and First Lady and a Medicine Show Man. In DAVE its a President and First Lady and 'comic' who is a party impersonator of the President. DAVE took its plot engine from a 1932 work.
Otherwise I could write a musical about two gangs fighting with star crossed lovers, and when the Laurents/Bernstein/Sondheim folk send a cease and desist, I can say 'No - this isnt based on West Side Story - its based on Shakespeare' That would be a hard sell.
