Two Kinds Of Commons
The social science literature on the commons was sparked by Garrett Hardin's classic article, arguing that common property inevitably leads to a tragedy as individually rational action leads individuals to overuse the commons. The bulk of social science reaction to Hardin's article, led by Elinor Ostrom, was based on the argument that the commons as Hardin describes it is not an accurate depiction of common property systems around the world. In most common property systems, some form of social organization -- most often Equality Matching, in which all participants are expected to make equal contributions to maintenance and are allocated equal shares of the produce or given an equal turn at using it -- explicitly limits exploitation. These authors concede that in the case of what is referred to as an "open access resource," such as oil, the Tragedy of the "Commons" plays out much like Hardin describes.
In discussing the Communal Sharing model, Fiske repeatedly asserts that common property falls under this model. And in fact his ethnographic descriptions of Communal Sharing among the Moose do resemble Hardin's open access rather than Ostrom's Equality Matching commons. No quotas are set on people's use of land or water, they are simply given free to anyone who asks. So why don't the Moose succumb to a Tragedy of the Commons?
I would suggest that there are actually two models of non-Tragic commons: the Ostromian and the Lockean. The latter gets its name because its features are suggested by Locke's account of property. Locke argues that appropriation of resources is initially limited by the inability to use more than a certain amount. There's no point in taking more apples than you can eat before they go bad. Locke says that this system will and should be superseded by the development of non-perishable, hoardable stores of value (namely money). With the ability to turn them into money, people can appropriate an unlimited amount of resources.
Among the Moose and other groups that use this system, the Lockean commons is spared from this monetary Tragedy by the very Communal Sharing ideas that underly the open access rule system. In a Communal Sharing situation, the boundaries between self and other are blurred. I do not think of you as another person with whom I must compete for resources, but as a fellow part of the larger group. So it makes no sense to hoard resources for the future use of my self -- and thus no rules limiting exploitation are needed. Each of us can take as much as we need, and the limits of our ability to use resources at once will (hopefully) be sufficient to keep the resource from being overexploited.
What the Tragedy of the Commons exhibits, then, is a dysfunctional system resulting from a mismatch between people's orientations (Market Pricing) and the social rules they encounter (Communal Sharing). But contra Hardin, the Market Pricing orientation is not universal.