Clearly Microsoft has a large stake as well. It sounds like equity was distributed to employees, but according to Fortune some was sold: "OpenAI’s other investors include Hoffman’s charitable foundation and Khosla Ventures. Last year, Sequoia Capital, Tiger Global Management, Bedrock Capital, and Andreessen Horowitz reportedly purchased shares from preexisting shareholders in a sale valuing the company at around $20 billion, according to The Information."
https://fortune.com/2023/01/10/microsoft-investment-10-billi...