> to prove that statement?
Cynically speaking, I am not sure that there is an audit you're going to be able to do that won't cost a ton of money that the people in this thread would trust as definitive "proof" of anything[0].
I think a big part of what I'm personally getting at with the comment above is that I'm not looking for perfect proof of anything; independent audits are great and I love to see them and I absolutely encourage them, but remember that the point of comparison here is Google/Bing. Take it with a grain of salt, and purely opinion me, but I think its fine for private search engines to offer the best proof of their claims that they can and to otherwise ignore people who demand perfection or nothing.
It's great to see more search engines in the space with a focus on privacy, and if you're able to pull off building your own indexes, that's also a pretty big win. I wish there was a more obvious path forward for your company to make money (I get nervous when companies say, "we'll figure out funding later", to me that comes across as a little bit of a time bomb). But in general, always good to see more private options for people available.
If I was in your position and I was looking for audits, I'd honestly be looking at the same sources that DuckDuckGo's founder talks about further up-thread, because that would at least allow me to say, "the same sources that claim DuckDuckGo is private have also said that we are private." But it's not my area of expertise, so maybe that's bad advice.
[0]: https://news.ycombinator.com/item?id=32586726