I don't see OpenAI as a member on https://thealliance.ai/members or any news about them joining the AI Alliance. What makes you believe they should be mentioned?
I meant more it's interesting that they're not a member or signed up to something led by big players in AI and operating for AI safety. You'd think that one of, if not the largest, AI company would be a part of this. Equally though those other companies aren't listed as members, as the sibling comment says.