Musk, the world's richest man, took the stand on Tuesday in a key trial over the future of OpenAI, describing his lawsuit against the maker of ChatGPT as an act to defend philanthropy.Musk is suing OpenAI, its co-founder and CEO Sam Altman, and president Greg Brockman, saying they betrayed him and the public by turning away from OpenAI’s mission to steward artificial intelligence (AI) with good intentions for humanity and turning the nonprofit into a profit-seeking behemoth.

Musk and Altman co-founded OpenAI in 2015 with the goal of developing AI to benefit mankind and compete with competitors such as Google. Thirteen months after Musk left OpenAI's board, the company set up a for-profit entity.

"If we allow a charity to be robbed, the entire foundation of charitable giving in the United States is going to be destroyed," Musk said during his testimony on the first day of the trial. "That's what worries me." The founder of Tesla TSLA.O and SpaceX also said that OpenAI is also his "brainchild."

"I did the idea, name it, recruit core members, teach everything I know, provide all the initial funding," Musk said. "It was expressly designed to be a charity that didn't benefit any individual. I could have turned it into a for-profit company, but I deliberately chose not to."

Before Musk began testifying, William Savitt, a lawyer for OpenAI and Altman, told the jury that it was Musk who saw an opportunity to make money when he funded OpenAI's early development and pushed it to transform into a for-profit enterprise, and he may even eventually become CEO. He said Musk wanted to "monopolize the power" and only filed the lawsuit after failing to do so.

Musk's lawyer, Steven Molo, told the jury in opening statements that greed was on OpenAI's part as the company brought in investors including Microsoft MSFT.O , which invested $10 billion in OpenAI in January 2023. "This is not a tool to get rich," Morrow said.

Musk is expected to continue testifying on Wednesday. He is seeking $150 billion from OpenAI and one of its largest investors, Microsoft, which will go to OpenAI’s charity arm. He also asked OpenAI to restore its non-profit status, remove Altman and Brockman, and remove Altman from the board of directors.