https://www.justice.gov/archives/jm/criminal-resource-manual...
For example, clearance of music samples.
Authors do not need licenses for works that inspired them.
In the "monkey selfie" case, a photographer named David Slater set up a camera in the Indonesian jungle, and a macaque monkey took a photograph of itself with it. When the photo was uploaded and shared, various parties began to argue over who held the copyright. Slater claimed it was his because it was his camera and he set up the situation. Others believed that if the monkey pressed the shutter, then the monkey, or no one, held the copyright.
The U.S. Copyright Office clarified its stance on the matter in the Compendium of U.S. Copyright Office Practices, Third Edition. It stated:
"The U.S. Copyright Office will not register works produced by nature, animals, or plants. Likewise, the Office cannot register a work purportedly created by divine or supernatural beings, although the Office may register a work where the application or the deposit copy state that the work was inspired by a divine spirit."