@ Sim: In several of the data download pages we list resources for further reference. In many cases they were used to inform the information shown in Natural Earth and in some cases they provide more information (in attributes and/or in line work detail) than we have. They should not be confused as the sole source for Natural Earth. Nor should they be construed as restricting the license of Natural Earth.
The short answer is if you’re in the United States, the public domain sticker holds true for all themes. If you’re somewhere else in the world, consult your local legal authority because of the following:
There are two cases in Natural Earth where the licensing needs a smidgen more work: Admin-1 and Marine Boundaries.
Admin 1 – States, Provinces
Admin 0 – Boundary Lines
For admin-1: the following columns are dependent on GADM (the remainder are facts readily available from multiple sources):
English type
valid from, and
valid to
The Natural Earth line work is completely original and the rest of the attributes are commonly available facts that are not copyrightable.
If you are concerned about the licensing on admin-1, simply delete these 3 columns from your copy of the file and proceed with no license restrictions. We’ve reached out to GADM to clarify this issue with them.
For the maritime boundaries:
The marine boundaries in Natural Earth use the VLIZ Maritime Boundaries Geodatabase that is listed in the reference section.
VLIZ is a open-source, public domain project. We do not include half the detail in terms of attributes or resolution as the original as this theme is not of general interest. We’ve slightly modified it so it matches up with our coastline and land boundaries. If maritime boundaries are of specific interest to you, the original VLIZ files are the preferred source. They also keep them more up to date than we will. We will clarify the license with VLIZ and report back.
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