If I were in the market for such a library, I'd still have serious concerns. The GPL license still appears in the root of the repo as if the entire codebase might be subject to GPL; It appears to be a fork of newlib (GPL) and that means it might not qualify as a "clean room implementation" of GPL'd code - the legal team in a corporation is going to insist on a ton of due diligence on Picolibc before they allow it to be used.
> Remove[d] unused code with non-BSD licenses. There's still a pile of unused code hanging around, but all non-BSD licensed bits have been removed to make the licensing situation clear. Picolibc is BSD licensed.
From my understanding, Newlib is a GPL-licensed project that has some GPL-licensed contributions and some BSD-licensed contributions (in the sense that these aren't original code written by contributors, but rather are copy-and-paste inclusions of pieces from various GPL- and BSD-licensed codebases.)
The author created Picolibc by (doing the moral equivalent of) cherry-picking out a small base of the commits to Newlib—all of which were copy-and-pastes from BSD-licensed codebases.
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In some sense, Newlib is very similar to how a Linux distro works, repackaging upstream code components (of various licenses) together.
Picolibc, then, would be a lot like creating a new Linux distro, derived "from" Ubuntu, that happens to use only the packages in Ubuntu that are themselves directly copied in from upstream Debian (pretending for a moment that Ubuntu does this rather than re-signing packages with their own keys.) Is such a distro really "derived from Ubuntu"? Or is it derived "from" Debian, with an Ubuntu mirror server just serving as a pipe that some Debian packages went through on their trip "from" Debian's hands "into" the hands of the new distro?
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Either way, worries that the GPL could infect this effort are misplaced—even if it comes to a legal battle, at any point, the same codebase could be recreated (with a bit of a schlep) by just going to all the same BSD-licensed upstream sources that Newlib's contributors pulled from, and doing the same copy-and-pasting that Newlib's contributors did.
