Hello, In my Smartphone I use f-droid.org for install app. F-droid is a market with open sources app (like BitTorrent Sync) https://f-droid.org/about/ Currently for use BitTorrent Sync I need download new release and I haven't auto update. I don't know what is you opinion about alternative marketplace in android phone but some CyanogenMod user do not install google app for use a full open source phone. You can add BitTorrent Sync at this market at this page: https://f-droid.org/forums/topic/adding-apps-with-git/