A green held in common by a village of peasants who graze their cattle there.
Grazing degrades the commons which re-grow their cover only slowly.
Possible Outcomes:
No grass left
An actor using coercive enforcing an allocation policy on behalf of the village
The commons will break up as village members each handle and protect its own part.
The open-source world, on the other hand has an "inverse of the commons" model.
Widespread use of free software tends to increase its value, as users fold in their own fixes and features. (so grass grows taller when grazed upon)
Raymond notes that keeping a patch to oneself, or trying to profit from it does not makes sense economically, and the best way to benefit oneself is to contribute it and integrate it with the existing codebase.