This package is already in the AUR, is popular, and appears to be libre.
It is a fork of Audacity after the relatively recent hostile takeover and series of fiascos, including adding spyware to Audacity and potentially violating the GNU GPL.
I think due to these reasons that it's also likely to replace audacity in the official Arch repos at some point.
(The version of audacity in the repos at the moment is currently unaffected by these issues, but might be once the package is updated, if that ever happens instead of it being replaced by tenacity.)