OpenAI disclaims ownership interest in the model output. If a subscriber (who has a contractual relationship with OpenAI) chooses to generate outputs that could be used to train a competing model, and chooses to share those outputs with third parties, that is not prohibited by the agreement. Further, the data being shared belongs to the subscriber and can be licensed however they desire (though actually, model outputs may not be copyrightable at all). If a third party who does not have a contractual relationship with OpenAI chooses to take this data and train a competing model, they are using the data under valid license and have breached no obligation to OpenAI.
Do you have the money to enforce such (dis)claims? That's really what it comes down to, you might be right but you'd go bankrupt in the process. It's simply better to just use something that didn't touch their outputs in the first place, like OpenAssistant.
