the continued airworthiness inspection criteria is required to be on all FAA Form 337s these days to keep the lawyers happy.
many times you will see the STC specifies a certian test or inspection be done at certian intervals to comply with the Continued Airworthiness Inspection.  In some cases there isnt anything to inspect as the componenant in question either works as designed or it doesnt.  so in that case the continued airworthiness is considered  "on condition"  on condition means ... if it is functioning normally its airworthy and no other inspection is required.  hope this makes some sense.
mark

Jim:

What you have here is an example of FAA order 8110.54, titled "Instructions for Continued Airworthiness"  The FAA requires all field approvals to have instructions on how to maintain the alteration that they are signing for.  There are several instances were an alteration will be listed as "on condition"  This simply means that there is no scheduled maintenance or inspections required, and that the only thing required is to repair the unit when it fails. 

Also, an expired data base does not make the unit unairworthy.  What would make the unit unairworthy is when is does not meet the TSO it was built under.  The same would apply when a manufacturer has service bulletins that can upgrade units.  You may decide not to perform the service bulletin, but that does not make your unit unairworthy, unless the service bullitin was required by an AD.   
Usually the flight manual supplement, or pilots guide will state that a current data base is required to perform IFR approaches.

Sal S       

Jim:
It is an operational aspect that would fall under FAR 91, (whoever OPERATES the aircraft must assure the data base is current).  That is why the manufacturer states that the accuracy is not assured unless a current data base is installed.

Dont confuse the TSO (technical standard order) is was built to, with operational requirements during flight.  The unit was designed and built to a TSO, this is what qualifies the unit as airworthy.  The unit itself just displays data from an external source which is inputed into the unit. 

The same as using charts or approach plates.  You cannot use old charts or approach plates that are expired.  I guess you could think of it as the data which would be unairworthy, not the unit!

Sal S