The way the story goes is that because MacOS, Windows & AmigaOS were all developed at the same time they couldn't sue each other for stealing ideas as they couldn't have. IBM came late to the party with OS/2, so they licensed some things.
Commodore got AREXX out of the deal, the irony is that all the time I ran OS/2 I never used REXX & I don't even remember it.
Commodore licensed ARexx from William S. Hawes. ARexx contains no code from IBM, why would you need a license from them for it?
IBM and Commodore had a cross licensing agreement. They didn't need to license anything, they already had access to all of Commodore's patents.
