I thought the joke was that OpenAI doesn't grant anything even resembling an "open" license (whether free as in freedom according to the FSF, open as in open source according to the OSI, or open as in Open Knowledge's definition [1]) to use OpenAI's models. (Tangential reminder: open is not merely access to the code and data but also the legal freedom to use and modify it for any purpose.)
[1] https://opendefinition.org/od/2.1/en/