An honest question: Isn't it that in some legal systems, an absence of license means public domain?
In general, unless you live in Burma or something, you can assume that if you don't have a license, you can't do anything with any content.
https://en.wikipedia.org/wiki/Copyright#Copyright_notices_in...
This change was because The Night of the Living Dead. http://en.wikipedia.org/wiki/Night_of_the_Living_Dead#Copyri...