Who audits the Renaissance numbers?
Meaning, which company other than Renaissance can vouch for their performance?
For like 10-15 years they had outside investors and returned most or all their profits every year so that the fund wouldn't get too large. Then they returned all the outside investors money in the mid 2000s so that they could keep the future profits for themselves. Simons went from nothing to being worth $20 billion, and all the other partners and scientists who have been there a while are fantastically wealthy. So, they are printing money there, and it's nothing like Madoff because they've paid out way more than they've taken in from outside investors.
They opened up a different fund that could manage up to $100 billion but doesn't have near the returns that the original fund has. That fund does manage $100 billion these days, but the returns aren't as good. The crazy performance of their original fund is partly so good because they cap the size of the fund at $10 billion. They've said managing more money than that would hurt performance.
I'm sure you could speak to plenty of other hedge funds who could vouch for their performance and would kill for their source code. As far as who their auditor is, I don't know.