"OpenAerialMap is an open collection of aerial photographs, collected into a single coherent view of the world."
License: Public Domain of CC Attribution.
"OpenAerialMap is a young project, and as such, many of the licensing restrictions are still being worked out. In the short term, all imagery uploaded to OpenAerialMap should be compatible with one of the following two licenses:
Creative Commons Attribution License
Public Domain (or the WTF PL), if you prefer."
Access: so-so. No way to get the data in bulk but you can browse the map. All code is store in svn.