It'd be hilarious that meta chose to pay openai. If there was such a deal, would it come to light in any public/official filings?

Depends on the size of the deal. OpenAI would have to disclose it in their S-1 if it crossed the threshold of being material information for investors.

Isn't S-1 just for IPO? Wouldn't it be in the 10-Q?

OpenAI isn’t public. It doesn’t file forms 10-Q.

No reason for it to. Software companies use products from other software companeis all the time.

meta already pays openai and anthropic for employee use despite having their own models available