OpenAI CEO Sam AltmanAndrew Caballero-Reynolds/AFP/Getty ImagesThere's an important stipulation on OpenAI's historic $6.6 billion funding round.The startup has two years to become for-profit, or it might have to give investors their money back.The process is likely to be complicated and could involve a battle in court, legal experts said.OpenAI's historically large $6.6 billion funding round is bringing in checks from some of the biggest technology and venture capital investors.But there's reportedly one condition on the round that could undo it all.If the ChatGPT-maker doesn't complete its transition to a for-profit company within two years, investors in the latest round could ask for their money back, multiple outlets have said.When it was founded in 2015, OpenAI was a nonprofit.