Defining the "Open" in Open Content
What does "open" mean? The word has different meanings in different contexts. Our commonsense, every day experience teaches us that "open" is a continuous (not binary) construct. A door can be wide open, mostly open, cracked slightly open, or completely closed. So can your eyes, so can a window, etc.
The "open" in "open content" is a similarly continuous construct. In this context, "open" refers to granting of copyright permissions above and beyond those offered by standard copyright law. "Open content," then, is content that is licensed in a manner that provides users with the right to make more kinds of uses than those normally permitted under the law - at no cost to the user.
Put simply, the fewer copyright restrictions are placed on the user of a piece of content, the more open the content is. The primary permissions or usage rights open content is concerned with are expressed in the "4Rs Framework:"