OAKLAND, California, April 30 : Elon Musk is due to return to the witness stand on Thursday for a second day of cross-examination by Sam Altman's lawyer, in a high-stakes trial over a lawsuit Musk brought accusing OpenAI of abandoning its mission to develop artificial intelligence for the benefit of humanity.  The world's richest man alleges that OpenAI, its co-founder and CEO Sam Altman, and its President Greg Brockman wooed his $38 million in donations by promising to build a nonprofit that