They probably misread the Wikipedia on OS/2, which says:
> In addition, IBM once made a deal with Commodore to license Amiga technology for OS/2 2.0 and above in exchange for the REXX scripting language.
In other words, IBM licensed REXX to Amiga in return for something else (we don't know what).
But who knows if this is true. Apparently IBM and Commodore already had an IP cross-licensing agreement at the time, and had access to their patents. And AREXX apparently did not contain any IBM code.
> In addition, IBM once made a deal with Commodore to license Amiga technology for OS/2 2.0 and above in exchange for the REXX scripting language.
In other words, IBM licensed REXX to Amiga in return for something else (we don't know what).
But who knows if this is true. Apparently IBM and Commodore already had an IP cross-licensing agreement at the time, and had access to their patents. And AREXX apparently did not contain any IBM code.