I was interested to read that there was a patent on 'non-round Compact Disks' but when you go to the actual patent application (
https://patents.google.com/patent/US5844757) the patent states "...The present invention relates to a method and apparatus for reading and writing information on a stand alone
magnetic card or disk typically adapted for use in standard three and one-half inch computer floppy disk drives." Note: I highlighted the magnetic part since Compact Disks are optical rather than magnetic. Not a patent lawyer but I'ld take my chances on not paying any royalty fees.
I guess that's why these days patents tend to be so broad and use language like "any and all means (present and future) of doing thing 'X' "