Open reuse Edit
Both the actual content of the conference and the design principles (of the gathering) are completely open (including for example not limited in their reuse in any way by copyright) for everyone to add to and improve. The design stuff - the design principles, and all experiential knowledge that people want to contribute from putting them into practice is share and share alike.
In practice this might be achieved by some sort of acknowledgement at the start of any process that all content and design materials are considered to be released under (for example?) the GNU Free Documentation License.
Open involvement and inclusion Edit
Although there may be circumstances when complete openness seems inappropriate, gatherings adopting OSCD will tend to be open and inclusive.
Circumstances when complete openness might seem inappropriate can include providing a sense of security for some participants who might not otherwise contribute or contribute as much, for example if there is any element of conflict resolution in the reasons for the gathering.
There is perhaps a sense in which participants adopting OSCD generally do not see conflict as inevitable.
Because of the presumption of openness OSCD gatherings would be unlikely to be inward looking and generally would be likely to adopt outward looking attitudes.