Com system or language?

The following is copied from a comment I made a while back over on The Languge Guy’s blog (here, specifically).

From the OSU Language Files (summaries in parentheses are mine):

All communication systems have some features in common:
1. A mode of communication (signal thru medium; signals may be visual, auditory, tactile or olfactory)
2. Semanticity (signals have meaning)
3. Pragmatic function (signals serve some useful purpose)

Some communication systems exhibit these features as well:
4. Interchangeability (individuals both send and receive messages)
5. Cultural transmission (some aspect of system learned thru communicative interaction)
6. Arbitrariness (form of signal not logically related to meaning)
7. Discreteness (complex messages composed of simpler parts)

True language has, in addition to the above, the following characteristics:
8. Displacement (ability to communicate about objects or events removed in space & time)
9. Productivity (system is open-ended: individuals can produce and understand novel messages)