This seems to be a misunderstanding by the author, a licence doesn't have to be copyleft to be free software. Even the FSF describes the MIT licence as a free software licence (they prefer calling it the Expat licence).
> Expat License (#Expat)
>
> This is a lax, permissive non-copyleft free software license, compatible with the GNU GPL.
> Expat License (#Expat) > > This is a lax, permissive non-copyleft free software license, compatible with the GNU GPL.
https://directory.fsf.org/wiki/License:Expat