Q. What is an implied license?

You can learn more about this on this box of the Copyright guide. 

Wikipedia has a great definition of an implied license.

An implied license, as an example, is involved with how we understand the "transmit requirement" when talking about embedding material. Learn more about the transmit requirement here.

The Fifth Circuit...court points to Field v. Google, which found an implied license where a website owner knew he could block Google from caching his pages with a meta-tag but deliberately chose not to. But notice the burden question that creates. In Field, Google raised implied license as a defense. - CopyrightLately