Anyone ever tried these as live food?

Not for my aquarium fish, but they were often used at trout hatcheries, before the development of commercially prepared trout foods. One of the locally hatcheries was established around 1890 as a private hatchery that raised trout to sell to the local passenger rail way. They would hang a carcass on a rope over the pond, and feeding consisted of smacking the carcass with a long pole so the maggots would drop into the hungry fish below.

For aquarium fish, I would not use them as a staple, since they are so high in fat. As a treat, or to getting fish into breeding shape, I can see no reason not to use them, other than the distaste of maintaining them. I would try using whole wheat bread and veggies instead of decaying flesh.