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By Deepa Seetharaman and Kenrick Cai

OAKLAND, California, April 30 (Reuters) - Elon Musk faced tense questioning and showed frustration on the witness stand on Thursday during a second day of cross-examination by Sam Altman's lawyer in a 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 person ‌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 would prioritize safe ​development of AI, before pivoting to create a for-profit entity to enrich themselves.

OpenAI has countered that Musk, the CEO of Tesla and SpaceX, is driven by a compulsion to control OpenAI and is bitter about the company's success after he left the board in 2018. They have also said he did not prioritize safety issues when he was with the company, and that he is trying to bolster his own AI company, SpaceX unit xAI, ‌which lags OpenAI in user adoption.

William Savitt, a ⁠lawyer for OpenAI, Altman and Brockman, pressed Musk on whether he had read a term sheet that Altman forwarded on August 31, 2017, relating to OpenAI's shift from a nonprofit to a for-profit overseen by a nonprofit.

"My ⁠testimony is I didn't read the fine print, just the headline," said Musk, wearing a dark suit, dark solid tie and white shirt.

'YOU CUT ME OFF'

At times, Musk expressed frustration with Savitt's cross-examination.

"Few answers are going to be complete, especially when you cut me off all the time," Musk said.

Thursday's exchanges ​echoed ​a tense cross-examination on Tuesday, when Savitt pressed Musk about text messages and ​emails showing that he at times expressed openness to creating ‌a for-profit entity and that Altman kept him apprised of Microsoft's investments in OpenAI.

Savitt is expected to cross-examine Musk for about an hour on Thursday, and a lawyer for Microsoft will also question him.

ChatGPT maker OpenAI, founded in 2015, has evolved from a nonprofit research lab in Brockman's apartment to a company worth more than $850 billion that is planning a potential initial public offering.

$150 BILLION IN DAMAGES

Musk is seeking $150 billion in damages from OpenAI and Microsoft, one of its largest investors, with proceeds going to OpenAI's charitable arm. Musk also wants OpenAI to revert to ‌being a nonprofit, with Altman and Brockman removed as officers and Altman removed ​from its board. Musk's claims include breach of charitable trust and unjust enrichment.

On Wednesday, ​jurors in federal court in Oakland, California, saw an email Musk ​sent to Altman and Brockman in 2017, referring to himself as a "fool" for providing them funding for what ‌he believed was a nonprofit venture.

"I felt like they ​had not been honest with me," Musk ​said under questioning by his lawyer, Steven Molo. "What they really wanted to do was create a for-profit where they had as much shareholder ownership as possible."

OpenAI has said it created a for-profit entity to allow it to accept private investments to help ​buy computing power and pay top scientists.

The trial started ‌on Monday and is expected to last several weeks. The next witnesses after Musk are expected to be his top ​aide, Jared Birchall, Brockman, and AI safety expert Stuart Russell.

(Reporting by Deepa Seetharaman and Kenrick Cai in Oakland, CaliforniaWriting ​by Luc Cohen and Nia WilliamsEditing by Rod Nickel and Will Dunham)