Presumably, without permission.
The app in question is called Monster Galaxy.
Specifically, it uses the blue and black wolf from inari's beads, Cathulhu, the yellow Gogh Reed monster, A gwee ripoff called a Pwee (Though it doesn't use the exact graphic like the others), Radio Jack, the pegasus from Faust's Bottle, The white and orange wolf from inari's beads, and an orange lizard-like thing also from the Gogh Reed (It could be something else, but this is what it looks like to me)
Some of the monsters, I recognize from Gaia, but I can't place exactly where.
Presumably, the other monsters they offer may have been lifted from Gaia or other sites.
Where can I report this?