Legal

SkyCharts v1.4.4 and greater is using RouteMe to display the maps.
Backend tools on linux use GDAL to create the maps.
Some icons are from Wikimedia Commons, like the P51 airplane silhouette, and states.

Other icons are from http://www.vectorstock.com/, http://icons.mysitemyway.com/ and  http://www.axialis.com/objects/ip_icon_08.shtml

Satellite Tiles Courtesy of MapQuest 
Portions Courtesy NASA/JPL-Caltech and U.S. Depart. of Agriculture, Farm Service Agency.

---