You don't have to have permission to use someone else's code, if it is open source. And I can't remember them specifically saying if they were using Android 5.0, but it was a while ago when they announced it would run on Android.
As do I. I have spent many a year debugging software as a security engineer so it is in my nature to over scrutinize everything. And as I recall the O.S was listed as being based off of Nougat 7.0.
News 
Market Data 
Discover 
