Okay. I don't really see the significance here. The US hasn't placed any restrictions on Israel here, and I wouldn't expect it to have done when it sold it.
Israel has a fair bit of US hardware in its inventory, so you'd expect to see that, and a JDAM is a pretty common weapon.
The US doesn't object to Israel fighting Hezbollah.
Like, there's no "gotcha" here.
It'd be odd if Israel had specifically avoided using JDAMs.
EDIT: And I'm sure that Israel's used plenty of US-made weapons aside from that. That bomb was probably dropped from an American-made aircraft. They were firing artillery in the conflict, and I'm sure that at least some of those rounds were American-made. It looks like Israel has a domestically-made Tavor issue rifle, but also a bunch of American-made rifles. Probably a long list of other items.
Until the Six-Day War of 1967, the Israel Defense Forces' principal supplier was France; since then, it has been the United States government and defense companies in the United States.
No, it is not. It's illegal to perform certain actions that kill civilians under the Geneva Conventions, but there is no blanket prohibition on killing civilians in war, which is why Hamas locating facilities under civilian buildings doesn't provide them with a legal shield.