It's listed on the Wikipedia entry, as well (not that that necessarily makes it true, I understand).
"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.[45] This means OS/2 may have code not written by IBM, which can prevent the OS from being open-sourced in the future.[46][47] On the other hand IBM donated Object REXX for Windows and OS/2 to the Open Object REXX project maintained by the REXX Language Association on Sourceforge.[48]"
http://en.wikipedia.org/wiki/OS/2
