Yes: https://platform.openai.com/docs/guides/chat . I wrote a small proof of concept plugin for vim last week, was quite easy to do with their Python library to access this API. I have no experience accessing the raw endpoints.
Not sure why I'm downvoted - I literally used it last week. I got an API key from my account and made several calls to it, using the OpenAI Python library.
I wouldn’t give much thought to it. Could be one random person.