Options will resolve YES as they happen or NO if they are not reported by the time OpenAI is trading as a public company. Things that happened before IPO but were not reported by trusted media sources (WSJ, FT, Reuters, NYT, The Information, etc.) or announced officially will not count. Market resolves N/A if no IPO by the end of 2028.

OpenAI says they haven't decided when to go public yet, since there are things they want to do "that are likely easier as a private company". I will judge what things are easier as a private company from my own subjective view and understanding, but if a resolution is controversial i might defer to a frontier LLM.
I will N/A added options that i consider to not be relevant to the private/public company question ("GPT-6 releases", "Sam Altman dies", "Trump says the words Obama or Obamacare")