Is it rotting? To be on the safe side I wouldn't feed eggs that have been sitting under a broody that long. But maybe someone else has done it and it's perfectly safe. Hope they chime in.
No. I imagine it would depend on how "ripe" they are. If they have been sitting around dead in the heat for several days and stink to high heaven I would think they would be full of bacteria. Of course, I have seen dogs eat some pretty stinking stuff. If the eggs are unhatched just out of the incubator and developed enough to know they only died a few days ago, I think they are still edible for dogs.