Everything in existence is composed of rivalrous and a non-rivalrous materials.
A wooden table contains the non-rivalrous Design that the worker applied to the physical material and the non-rivalrous design of the genetics that transformed the water, soil, sun and rotting matter into a tree.
The table is also rivalrous in that there is a limited number of (copies of) that type of table in existence at any one time - even though the potential number is limited only by the truly finite properties of nature such as Space, Time, Mass, Energy, and applied Work.
Software, music, video, text and other apparently non-rivalrous things are just as limited as the table by the physical mechanisms required to create, store and express them. This tends to be overlooked because these costs are usually quite low (storage, bandwidth, electricity), but is more clear when you scale it up to larger operations with heavier data such as video or GNU/Linux distribution sites. --Ownut 10:36, 6 January 2008 (PST)