Openness
Openness, in the context of peer production, governance and property, refers generally to the availibility of the raw material for the social cooperation to occur. If such material is indeed "open", then it means that individuals and communities are "free" to use and modify it.
The open/free paradigm is part of the three processes that are necessary for the social reproduction of peer to peer processes, see the Circulation of the Common
More Information
See the defintion of Open Knowledge and of the Free Software Principles