Is it a first step towards acquiring/merging OpenAI with one of his companies? He's offered it to buy once before, in 2018 [0]. (He's also tried to buy DeepMind—page 10 the OP filing).
[0] https://www.theverge.com/2023/3/24/23654701/openai-elon-musk... ("Elon Musk reportedly tried and failed to take over OpenAI in 2018")