If you mean something like self hosted, it would be really easy, but no one would use it. Imagine you order a burrito and the guy just eats your burrito, and you can’t do anything about it. Or imagine you’re a driver and you deliver the food, then don’t get paid. You need a business in between to take the liability for anyone to trust it. It being open source wouldn’t really matter, because you need massive capital and infrastructure to make it work.