Appstream metadata, which is canonically provided by upstreams and is
distro- and package-type-agnostic (available in at least apt and Flatpak),
has this as an optional field for self-rating:
https://www.freedesktop.org/software/appstream/docs/chap-Metadata.html#tag-content_rating
https://hughsie.github.io/oars/
I suspect that's the only way this could possibly work without money
changing hands.
There are no age classifications, however.
So based on content_rating tag on AppStream metadata, we can add logic to apt in order to determine age rating for our
packages. However, external review (maintainers) may be need in order to prevent misleading information on
content_rating.