The blog posting mentioned above is now at:
https://www.esri.com/arcgis-blog/products/arcgis-living-atlas/mapping/living-atlas-subscriber-conten...
As it explains, some layers in the ArcGIS Living Atlas called "PREMIUM" are proprietary to outside data providers and partners and require a separate subscription if you want to use them or publish them for public access. Others called "SUBSCRIBER" may have other limitations put on by the data provider that require an organizational subscription to access.
