I was reading in the GLORIOUS ONES Playbill from Pittsburgh that Lynn Ahrens actually started working on that Commedia dell'Arte musical (at that time with another collaborator in the BMI Workshop, not with Stephen Flaherty) in 1983. That collaborator subsequently gave Lynn Ahrens her blessing to pick up the project with Stephen Flaherty. So Lynn Ahrens' involvement with adapting a novel about Commedia dell'Arte seems to date back to 1983. Noel, is it possible you were working on your Commedia dell'Arte musical with Tony Kushner around the same time, since yours appears to have first been seen in a university production in December 1983? If so, again, it seems there's no need to be concerned that anyone copied your show's idea. And of course, their show is based on a novel that predated 1983.