To add, when you depend on any other crate, you are responsible to comply with the license terms of the crate, plus the license terms of any of its dependencies (and recursively all the way down).
Example, if you have a crate awesome_app, and you depend on apple_counter , and apple_counter depends on counter , then you must comply with licenses from both those crates.
Alludes to security vulnerabilities as well -- you are responsible for the security of your code, and of all code that you use.
Oh ya, no one really realizes what they use until they go and look, which is why I recommend setting up CI to check the licenses of all your dependencies against a whitelist (e.g. to make sure you don't accidentally pull in an only-GPL license crate)