So, how do you get the license of a image? Seems there is no straightforward way.

For example, http://commons.wikimedia.org/wiki/File:Turner,_J._M._W._-_The_Fighting_T%C3%A9m%C3%A9raire_tugged_to_her_last_Berth_to_be_broken.jpg is in the public domain.

Thanks,
Zhao