• Elon Musk is suing Sam Altman and Greg Brockman over his charitable donations to OpenAI.
• Brockman, an OpenAI executive and cofounder, took the witness stand on Monday.
• He was asked about his wealth and OpenAI's IPO plans.

The trial for Elon Musk's lawsuit against Sam Altman started up again after a weekend break.

On Monday, the Oakland, California, federal courthouse saw testimony from Greg Brockman, OpenAI's president, who is a co-defendant in the case. Jurors also heard testimony from Stuart Russell, a prominent artificial intelligence scientist whom Musk hired as an expert witness.

Brocman is expected back on Tuesday. Shivon Zilis, a former OpenAI board member and mother to some of Musk's children, is also expected to take the witness stand this week.

Here are the biggest takeaways from the trial on Monday, drawn from witness testimony and evidence presented in the California federal court. It is also the first day the trial was streamed on YouTube.

Greg Brockman is officially one of the richest people in the world

Under questioning from Musk's lawyer Steve Molo, Brockman said he owns nearly $30 billion in OpenAI shares. Those shares alone would rank him somewhere in the 80s or 90s in Forbes's list of the wealthiest people in the world.

Brockman also said he has $471 million in shares of Stripe, where he served as chief technology officer before becoming an executive at OpenAI, among other investments.

Brockman said he'd donate $100,000 to OpenAI's charity — but didn't

Brockman's testimony kicked off with an email he sent to Marissa Mayer back in 2014 when she was still CEO of Yahoo. In it, he told her about the AI lab he was starting with donations from Silicon Valley bigwigs like Elon Musk, Reid Hoffman, and Peter Thiel.

Brockman said he was "personally donating" $100,000, it emerged in court on Monday. Brockman made the same claim to other potential donors, but never came through with the money, he acknowledged under questioning by Musk's lawyer Steven Molo.

In explaining the delay, Brockman put the onus on Altman: "I asked Sam when I should donate this, and he said he would let me know."

Brockman confirms OpenAI is exploring a public offering

In his testimony, Brockman confirmed publicly for the first time that OpenAI was exploring an IPO for OpenAI.

"You are exploring the possibility of doing something called an initial public offering, is that right?" Molo asked Brockman.

"I think it's possible," Brockman said.

"You're exploring it, aren't you?" Molo asked.

"I believe so," Brockman said.

If OpenAI were to go public, its initial public offering would be one of the biggest in history.

The current record for the biggest IPO is Saudi Aramco, in 2019, at about $29 billion.

OpenAI's most recent round of fundraising put its private valuation at about $850 billion.

Anthropic and SpaceX are also reportedly considering IPOs this year.

Elon Musk asked Greg Brockman to settle the lawsuit 2 days before the trial

Shortly before court opened for the day, lawyers for the OpenAI defendants revealed in a court filing that Musk reached out to Brockman two days before the trial began to gauge his interest in a settlement.

Brockman suggested that both sides drop all their claims. Musk didn't appear satisfied.

"By the end of this week, you and Sam will be the most hated men in America," Musk responded, according to the filing. "If you insist, so it will be."

The lawyers for Brockman, Altman, and OpenAI asked US District Judge Yvonne Gonzalez Rogers to allow the communications to be entered into evidence. She hasn't ruled on whether the jury will be allowed to see them.

Elon Musk's very expensive expert witness

The first witness to testify on Monday was Stuart Russell, an artificial intelligence expert who teaches computer science at the University of California, Berkeley.

The most memorable part of Russell's testimony was when he talked about how much Musk's legal team paid him. He received an eye-popping $5,000 per hour for 40 hours of preparatory work. Expert witnesses in high-profile cases typically make between $500 to $1,000 per hour.

Russell testified he was making $235,000 altogether from his work on the trial, which he said amounts to about 20% of his income this year.

He is being paid by Excession, which is Musk's family office, he said.