I find it a bit strange that the rewrite is licensed under MIT. Are they doing a clean room reimplement or are they rewriting the core utils by looking at the source code?
Sure, but they'll also have an easier time of ensuring they're "pretty close" to fully reproducing the original.
At least, in comparison to having to reverse something black box. :)
Rust coreutils replacing GNU coreutils in these programs by implementing the same interface is the same issue.
I’m not sure if it’s possible to spell it out clearer than this.