Welcome to the forum, we love new people here. 
Food safe? Almost no burned plastic is going to be food safe. There are a lot of nasty byproducts to burning plastics that I wouldn’t want to ingest.
As for glowforge safe, this plastic add-in is the question. Without knowing exactly what plastic it is you’re taking a risk that it might contain chlorine or other ingredients that might form vapors that could harm your glowforge. I’d try to find out exactly what plastic (resin) they’re using and go from there.
For some more information on materials and risk, check out #4:
Particularly take note of the chemical risk section and the do not laser lists at the bottom.