Now that you mention it, I think it should even be part of C.
If I am developing a GNU project, I am likely publishing it,
so I would be disappointed if GNU were to recommend a host
without this feature. Also, I believe it to be very easy
to implement this freedom-supporting feature, so lack of this
feature would be a sign that the host is against freedom.
Instead of talking of authentication, we could say something
about the practicality for a free package manager project of
incorporating the code hosting repository as the dowload source
for source code repository for a free operating system; that is,
the code hosting repository being rated (for example, Savannah)
needs to provide the source code in a way that a package manager
(for example, Hyperbola packages) will accept it. This is not
the main purpose of publishing the source code as within the repository,
but this one has strict requirements relative one-off downloads.
Wording could be something like this:
Can be used as the package's canonical source in a free package manager,
e.g., without authentication, API key, or CAPTCHA.