[Sender]

Wonder what these grill-like items are on the back end of the MOAB?
Guidance vanes or maybe release vents for the fuel load?

[Saturnalia]

Those are the guidance fins, they deploy after release.

[Justin Thyme]

I believe it's referred to as a "retarded" bomb, and no, I'm not picking on it's IQ. ;)

Retarded bombs have restraining fins to create drag, and give the bomb a more predictable flight. In this case, I believe they can also be used to steer.

[ArrogantBustard]

They are guidance vanes. After drop, those vanes fold out perpendicular to the bomb case. Each vane is a composite of many small vanes which are adjusted by the guidance system to steer the bomb. It also has stubby winglets in the middle. And MOAB, contrary to (unfortunately) common belief, is not a fuel-air explosive. It contains 18 tons of tritonal explosive. Tritonal is a mixture of TNT and aluminum powder (80/20 IIRC). FAEs don't work very well past a certain size, which is much smaller than the MOAB. Proper dispersion of the fuel becomes difficult or impossible.

[Pontiac]

Have a look at what is going to Iraq.