Yes, hotglue is quite safe and hasnt burnt any of my plants. Do a google specifically for fishtanks if you wish. I just dab on small drop size portions and when they start to cool off, I simply hold and align the plants in place till it sets. Quick, simple and easy but it doesnt adhere that well onto smooth surfaces.
Ive only used hot glue for sticking anubias or java fern onto wood or rocks but these plants are quite tough. Fontanalis (java moss) should be fine too but since its light, superglue might work. (I sometimes use superglue as emergency sutures on larger fish or to close gaping wounds).
A couple of useful links for starters
Is Hot Glue safe for fish?
Quick Guide to using Hot Glue