CELESTIA
The free space simulation that lets you explore our universe in three dimensions. Official Webpage http://www.shatters.net/celestia/
License Issues
Models and Textures used in Celestia and its licenses. Please keep on mind that it is early version since I did not have any answer from author assuring that this models/textures are still used in newest version Celestia. http://wiki.debian.org/DebianEdu/Celestia/license_issues