Does MAF cleaner harm my engine if it gets into the intake

It should be fine. Mass Air Flow cleaner is pretty mild compared to carb cleaner and I have seen many people run their cars at high idle and spray tons of carb cleaner down a carb. So, a little MAF cleaner is pretty mild stuff and if you did not spray tons of it or have it revving to 3000 RPMs, chances are your okay.

I still don't think it would do any damage as it is less caustic than carb cleaner as the MAF is made up of sensing wires about the gauge of human hairs in many cases. So the engine would tough to damage with it as the worst it might do is to stall the engine. Especially as long as you were not revving the heck out of it it would stall the motor probably as it is not caustic enoguh to burn in engine.