Sam Altman and Elon Musk Getty Images Elon Musk was back on the witness stand in his civil trial against OpenAI and its CEO, Sam Altman. Musk's money manager, Jared Birchall, testified about Musk's charitable donations. See who will be questioned next week when the trial continues. Day Four of the blockbuster civil trial in Elon Musk's lawsuit against Sam Altman began Thursday with Musk returning to the witness stand. Musk faced grilling by OpenAI and Altman's lead lawyer, William Savitt, and a brief round of questioning by an attorney representing OpenAI backer Microsoft , also a defendant. Jared Birchall, a former Morgan Stanley banker and Musk's money manager, was the second witness called by Musk's legal team. Here are the biggest takeaways from the trial, drawn from witness testimony and evidence presented in the California federal court.…