These flags are downloaded from the CIA factbook, which can be found 
at: https://www.cia.gov/cia/publications/factbook/

The images are PNG files rescaled to a height of 18 pixels (one third
the original size) and named after the 2-letter ISO 3166 code of the 
country/region (instead of their FIPS code on the website), see the
file codes.txt.

These images are in the public domain as stated on the CIA fackbook 
website at:
https://www.cia.gov/cia/publications/factbook/docs/contributor_copyright.html
