"Nonprofit" is just a tax and wind-down designation (the assets in the nonprofit can't be distributed to insiders) - otherwise they operate as run-of-the-mill companies with slightly more disclosure required. Notice the OpenAI nonprofit is just "OpenAI, Inc." -- Musk's suit is akin to an investor writing a check to a robot startup and then suing them if they pivot to AI -- maybe not what he intended but there are other levers to exercise control, except it's even further afield and more like a grant to a startup since nobody can "own" a nonprofit.