OAKLAND, CALIF. — Microsoft CEO Satya Nadella took the witness stand Monday in Oakland, California, in a trial over control of the artificial intelligence startup OpenAI, defending the company's for-profit structure and Microsoft's investment. He was the third tech billionaire to testify in the lawsuit in as many weeks.

The lawsuit centers on Elon Musk's claims that OpenAI has strayed from its original mission as a nonprofit research center, with allegations that Sam Altman and Greg Brockman enriched themselves at the expense of what was supposed to remain a charity. Microsoft is a co-defendant through its partnership with OpenAI. Musk alleges the company aided OpenAI's breach of charitable trust when it turned into a for-profit. Microsoft says it was not aware of any conditions Musk might have placed on his charitable contributions and did not intend to encourage Altman and Brockman to violate their duty to OpenAI's nonprofit mission.

"Without a for-profit entity, it would be hard for OpenAI to pursue its mission," Nadella said. He also told the jury, "OpenAI had all the rights and resources they always had."

In 2019, Microsoft agreed to invest $1 billion in OpenAI's for-profit arm and provide cloud computing services in exchange for rights to a share of profits and an exclusive license to commercialize one of OpenAI's models for a year. The company added another $2 billion in 2021 and $10 billion in 2023 after OpenAI had released ChatGPT. Microsoft obtained a 27% ownership stake in OpenAI following the startup's restructuring. Planning documents from 2023 showed the company hoped to reap a $92 billion return on its initial $13 billion investment, and OpenAI's valuation reached $852 billion in March 2024, putting Microsoft's stake at around $135 billion.

"It's worked out very, very, very well for Microsoft, hasn't it?" attorney Steven Molo asked. Nadella responded in the affirmative.

Nadella also addressed Altman's brief ouster as OpenAI CEO in November 2023. "That was obviously very concerning to me," he said. "Given all of that competition, I just wanted to make sure we could hang on to the band that created all this technology," he added.

Pre-trial evidence included notes from an October 2020 meeting recording that Nadella discussed Musk's perspective on a "closed" OpenAI and said the matter was worth thinking through after expressing a desire not to get drawn into the dispute. U.S. District Judge Yvonne Gonzalez Rogers cited the notes as one piece of evidence for sending the accusation against Microsoft to trial. Emails from 2018 showed several Microsoft executives said they had made visits to OpenAI and were not seeing imminent breakthroughs in developing artificial general intelligence.

Altman was scheduled to testify later in the week, with the jury scheduled to hear closing statements Thursday.