Billionaire Elon Musk took the stand on Tuesday to accuse OpenAI and its boss Sam Altman of betraying the AI company's altruistic origins, in a trial that could have far-reaching consequences for the industry and oblige the ChatGPT maker to profoundly revamp its business.

The legal clash across the bay from San Francisco is widely seen as a battle of egos, pitting the world's richest person against a startup Musk once backed and now trails in the booming AI sector.

Central to the case is Musk's claim that Altman steered OpenAI into a profit-driven juggernaut aiming to rival giants like Google, Apple and Microsoft, abandoning its original nonprofit mission.

"If a verdict comes up that effectively makes it okay to loot a charity, the entire foundation of charitable giving in America will be destroyed – that's my concern," Musk said on the stand after being called as the trial's first witness.

Musk said he backed OpenAI as a nonprofit to ensure AI benefited society, with all technology open source.

"I didn't want to pave the road to hell with good intentions," Musk said of his vision for OpenAI. "I didn't want to fund OpenAI to make safe AI and then find out that it was actually making unsafe AI."

Musk also said he was instrumental in recruiting key hires, including Ilya Sutskver, a top AI engineer, then at Google, who went on to play a major role in driving new technology at the lab.

The world's richest man said he also made initial contact with AI chip maker Nvidia and tech giant Microsoft to provide crucial technology, opening doors that would not have been available to OpenAI's other co-founders, who were little known at the time.

'Anything to attack'

Altman and Musk co-founded OpenAI in 2015, promising a nonprofit lab whose technology "would belong to the world."

Musk invested at least $38 million before leaving in 2018, and the OpenAI Foundation launched a commercial subsidiary the following year. Microsoft then invested $13 billion, now worth about $135 billion.

William Savitt, the lead attorney for OpenAI, said in opening remarks that the company had no choice but to open up to outside investors given the high costs of AI and that, in any case, the OpenAI nonprofit arm "remains in control of the organization."

Savitt added Musk "will do anything he can to attack OpenAI" out of regret for having left the project.

Since his exit, OpenAI has grown into an $852 billion AI superpower and is preparing for a high-profile IPO on the back of its ChatGPT chatbot, which took the world by storm in 2022.

Musk eventually set up his own lab, xAI, which he merged into SpaceX in February. SpaceX is valued at $1.25 trillion, with a potential historic IPO in June.

Before opening statements, Judge Yvonne Gonzalez Rogers instructed Musk and Altman to limit social media posts. Musk mocked Altman on X, calling him "Scam Altman."

By late May, the judge, guided by the advisory jury, will decide whether OpenAI broke its promise to Musk or simply capitalized on its technology. Musk seeks a return to a pure nonprofit and the removal of co-founders Altman and Greg Brockman. He has claimed up to $134 billion in damages but pledged any award to OpenAI nonprofit.

(With input from AFP)