Open source != peer review

I wrote an essay on why I don't agree with the idea that good peer review requires open source. Why is the right to redistribute, on top access to the source code, needed for peer review?

My followup question, once you've answered the first, is to explain how I can review source code and not be accused some time in the future of using that source code in my own code, in violation of copyright and license agreement. This can occur even with free or open source licenses, for various reasons.