Rewriting "any software" is an extremely high bar to begin with. I think, we can agree that smaller utilities and libraries can be rewritten by anyone.

Another comment [1] even references the "Bram's Law". It basically says that any piece of software that's easy to rewrite will be rewritten countless times (and most rewrites are going to be bad)

[1] https://news.ycombinator.com/item?id=44606219