To me OpenAI's response is simply, "It is our honestly held belief that given our available resources private partnership was the only viable way to ensure that we are in control of the most advanced AGI when it is developed. And it is our honest belief opening up what we are developing without a lot of log term due diligence would not be in the best interests of humanity and the best interests of humanity is the metric by which we decide how quickly to open source our progress."
To me you can't win a lawsuit like this that is essentially about a small difference in opinions about strategy, but I am not a lawyer.