CITIES:

The data in the cities.txt file consists of data that was available in 

http://www.world-gazetteer.com/st/popdata.zip

and is now available in a more recent version at:

http://www.world-gazetteer.com/dataen.zip

It's reduced down to all entries which provide lat/long data and which describe places with > 15.000 habitants with simplified names. License from

http://bevoelkerungsstatistik.de/wg.php?x=&men=ipge&lng=de&dat=32&srt=npan&col=aohdq#copyright

Informationen zum Copyright
alle Daten © 2005 by Stefan Helders
Dieses Projekt soll als frei verfügbarer Datenlieferant dienen. Einige Anfragen veranlassen mich dazu, die Informationen zum Copyright zu präzisieren. Wer die Daten oder Grafiken auf seiner eigenen Website oder in einem Buch benutzen will, sollte nach Möglichkeit folgenden Hinweis unter den Daten oder im Quellennachweis verwenden: © by Stefan Helders www.world-gazetteer.com

Translation:
Copyright information
all data © 2005 by Stefan Helders
This project is meant to be a freely available data provider. Some requests make me specify the copyright information more precisely. If you want to use the data or pictures on your own website or in a book, please add a note as follows if possible: © by Stefan Helders www.world-gazetteer.com

The data for the Czech Republic were updated using the public database of the Czech Statistical Office which holds the copyright on them. It is permitted to reuse the data as long as the CzSO is mentioned as the source.
See http://www.czso.cz/eng/redakce.nsf/i/home

OCEANS:

The ocean data inside the "boundaryplacemarks.kml" was taken from the CIA World Factbook which is placed in the public domain.