Licenses

GADM's license is very restrictive. We are free to use the downloaded data for personal and research purposes but we cannot redistribute it or use it in commercial settings. Technically, it isn't open source data as it does not give the four freedoms of using, modifying, redistributing the original version, and redistributing the modified version without restrictions. That's why the example dataset doesn't contain GADM's version of Luxembourg.

GeoNames has two datasets--a commercially licensed premium dataset and an open source one. The open source data can be used for commercial purposes without restrictions.