Billionaire entrepreneur Elon Musk expanded his lawsuit against ChatGPT maker OpenAI, adding federal antitrust and other claims and adding OpenAI’s largest financial backer Microsoft as a defendant. Musk’s amended lawsuit, filed on Thursday night in federal court in Oakland, California, said Microsoft and OpenAI illegally sought to monopolize the market for generative artificial intelligence and sideline competitors. Like Musk’s original August complaint, it accused OpenAI and its chief executive, Samuel Altman, of violating contract provisions by putting profits ahead of the public good in the push to advance AI.