Some of the answers:
1. It could be honey. Check to see if there is a crack outside that bees are coming in and out of. – I’m a beekeeper. This is not impossible, but from what I’m seeing, it would be very unlikely. Honey is stored in comb, and when it is released, bees from far and wide will come to clean it. The way it’s clinging to the ceiling also makes this unlikely to me. But, that said, it is not quite impossible. You’d have to check to see if there is bee traffic in and out of that wall to the outside. I do frequent cutouts — from structures and trees alike — and I just have real trouble imagining that much honey sitting out without frenzied bees all over it.

-I’m an archaeologist and I wonder if this is resin from overgreen wood? But there’s a lot of it.