- document criteria for whether a license is hidden
- needed for license spectrum on /licenses OR
- on 'popular' list at https://opensource.org/licenses (some other list could be used in the future)
- adjust license properties and tests accordingly
This gets non-hidden list back close to what it was before #386 and (pending licensee vendoring this change, licensee release, and github.com licensee dependency version bump) some commonly requested licenses (eg #413#449) will reappear in the github.com license drop-down.