There may well be much healthier stuff in their dumpster than peanut butter and jelly. Why not offer to make an arrangement with the person in question to let them take stuff that's about to expire? Or, like, separate food that's being marked out into its own bag and maybe even put it in a cooler or something?
There was a time in my life when I did a fair bit of this myself and I was mostly getting like prepared foods that had been marked out the same day I was getting them. Peanut butter and jelly would have been a downgrade from pulling a couple of days worth of meals with like meat and cheese and veggies and stuff rather than just sugar and nuts and bread.
Not to say that this isn't nice, but it may well be a less viable option on its own in the long term. I suppose they could always do both.