A former OpenAI board member has explained how her unconventional personal relationship with Elon Musk evolved into having four of his children.

Shivon Zilis testified in a federal courtroom in Oakland, California for hours on Wednesday as part of Musk's lawsuit trying to reverse OpenAI's change to a for-profit company.

The focus of Zilis's appearance was her direct involvement in early talks with Musk around the company becoming a for-profit, but also how she worked for and became involved with Musk as she advised OpenAI.

"I still really wanted to be a mum and Elon made the offer around that time and I accepted," she said, explaining Musk in 2020 had offered to donate sperm.

"He was encouraging everyone around him at that time to have kids and he'd noticed I did not. He offered to make a donation," Zilis said.