Unfortunately, IP law doesn't really help when the platform owner can just say 'no' and cut off your entire revenue stream, perpetually. While you might have the law on your side regarding the IP, Apple seem to have the law on their regarding their right to cut you off. For small Apple only businesses, this is essentially a "license to kill", and you have no recourse but - possibly - to cause enough bad publicity.
Pretty sure Clue were not the first people to figure out how to track things with a database. I wouldn’t be surprised if they weren’t even among the first 100 period trackers in the iOS App Store.
