Small Transport; Low Wing; 2 Turbojet Eng
Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor; Flight Crew Multiengine
Flight Crew Last 90 Days 150; Flight Crew Total 10000; Flight Crew Type 1500
Situational Awareness; Other / Unknown; Communication Breakdown; Confusion
Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural FAR; Ground Event / Encounter Other / Unknown
General None Reported / Taken
Human Factors
Runway 23 at MMU has a temporary displaced threshold due to construction.  Referencing FAA publication Aeronautical Information Manual (AIM) the portion forward of yellow chevrons is defined as part of the TODA (takeoff distance available) measurement and is located behind the landing threshold. We positioned the Transport category aircraft forward of the yellow chevrons and behind the displaced landing threshold for takeoff in order to assure sufficient TODA vs computed BFL (balanced field length). Nowhere in the NOTAM was there reference to TODA being measured in a manner contrary to the depiction in the AIM. The Tower claimed our takeoff was started behind the displaced threshold. We believe that the displaced threshold is only applicable to landings based on the description and illustrations in the AIM and therefore is not applicable to takeoffs. Our takeoff was started at the beginning of the measured TODA as described in the FAA publication.
Small Turbojet Air Taxi Captain reported unknowingly taking off from a portion of the runway that was closed at MMU airport.