JAR-OPS MEL Policy Document (the baseline document for all operational equipment) would have allowed the flight to launch with a RADALT unserviceable:
(O) May be inoperative provided :
(a) It is not reasonably practical to repair or replace
the Radio Altimeter before the commencement
of flight,
(b)No more than 6 hours shall be flown over water
since the Radio Altimeter became unserviceable,
(c)Not more than 24 hours have elapsed since the
Radio Altimeter became unserviceable,
(d)The aircraft shall not fly overwater at an altitude of
less than 500 feet except for take-off and landing,
and
(e) The helicopter shall not descend below 500 feet on
approach to landing overwater unless the landing
site is clearly visible to the pilot.
Cannot find an entry in the FAA MMEL (could signify that it is not permitted to be unserviceable; or, it is not considered - period).