Edits and fixes based on review.

Docker-DCO-1.1-Signed-off-by: Fred Lifton <fred.lifton@docker.com> (github: fredlf)
Following that link, I came upon this page (http://www.gnu.org/licenses/license-list.html#Expat), which also has a short description of alternative licenses. Maybe worth adding ("for a list of alternative licenses that can be used look here...")?