OpenAI cofounders Sam Altman and Elon Musk are in the middle of a court battle. Getty Images Sam Altman is throwing a party to celebrate OpenAI's GPT-5.5. Altman said Elon Musk could come 'if he wants.' The two AI leaders have a long-standing feud and are in the middle of a federal legal battle. After battling it out in court this week, OpenAI CEO  Sam Altman  made a surprising, if not full-throated, gesture to his rival, Elon Musk, on Saturday. OpenAI is planning a small celebration on May 5 for the release of its latest model, GPT-5.5. Altman shared an online form for those interested in attending to RSVP, and said Codex, OpenAI's coding agent, would help the company choose people from the replies. Registration closed quickly, and Altman later said that he'd plan bigger parties in the future.…