Openness for APIs is about to be Accessible, to be Public, to be Neutral and to be Re-usable without restrictions.
So to be Public is one of the part of to be Open, in my opinion of course.
Some people have made a larger definition about openness http://opendefinition.org/okd/
It is the last one of openness requirements ("Re-usable without restrictions") that bothers me. However I realize that other might understand the title as intended... In other words, I should probably add "YMMV" to my original comment. :)
Openness for APIs is about to be Accessible, to be Public, to be Neutral and to be Re-usable without restrictions.
So to be Public is one of the part of to be Open, in my opinion of course. Some people have made a larger definition about openness http://opendefinition.org/okd/