The advantage of POSIX coreutils is their portability and universality; I can expect them to be present on any POSIX system. If re-writing will sacrifice portability, _we might as well do a clean break from POSIX and seek to improve upon existing coreutils_ rather than replace them. I listed some on [my "uses" page]({{<relref "/about/uses.md">}}): Zsh+DASH, ripgrep, sd, and fd. Three of those are written in Rust.
> release them with a better licence
I actually do like copyleft for more substantial works. However, POSIX shell utilities have been implemented many times over: Busybox, Toybox, and FreeBSD utilities come to mind. The specific free license they use is no longer important.
