OK.
Two points:
1) You can always land ... you just might not like the results. A modern jetliner, such as a B-787, with a full load of fuel can take off at a heavier weight than it should land. Such was the case with this aircraft. I agree that landing whilst overweight is inadvisable.
2) Since first posting, I have learned that the B-787 can dump fuel. Not all jetliners have this capability. My point here is that the aircraft flew around for 30 minutes on one engine, while above maximum (approved) landing weight. That is a testimony to the good design and construction of the aircraft.
I listened to the ATC audio linked at the NY post website article. The flight crew was pretty darn sharp and professional. They have to run checklists for engine failure.
Dulles ATC was on the ball as well...