Hi !
(FYI : I have 2 five-year-old gliders, and I've never feed them aloe vera.)
I think both of the answers can be true !
I know plenty about plants and their medicinal use / toxicity : it depends on the dosage AND the application !
So, in the case of the aloe vera for gliders, my guess is that its external application is ok, but an "internal application" (ingestion) may not be ^^
I checked : it's bad !! toxic for the digestive system : the aloïne is tolerated at a rate of 0.1mg/kg in humans and only for a limited duration like a week. There, if you're interested by the details (it's in french but Google translation should do the trick !) :
www.aloemagazine.com/aloine-et-seve-aloe-vera/
In a nutshell : don't put your gliders in contact with aloe vera as the whole plant.
For aloe vera as juice sold in supermarket, maybe check the composition : gel, not sap, and free of aloïne >> if so, it should be ok to ingest.
I would advice you to try a tiny amount some night, then pay attention to the reaction of the glider and its stool for 1 day ! Anyway, it's not gonna kill it, but it might make its stomach hurt a bit or make its stool close to liquid.
If so, you'll know aloe vera is not for your gliders !
If not and they seem to appreciate the juice, I think you can keep giving them some as treat or as part of their meal :)