Get a list of the licences of all packages on Ubuntu system [closed]
The answer to this question suggests that automatically pulling the license info out of a single .deb package is non-trivial.
I suspect there is no easy way to do what you want.
Since the answer I linked to has been updated, I'll update mine too.
This is beginning to change, as the
debian/copyrightfile is now required to be machine-interpretable, so you can look forward to this in the future.