It seems the question of the moment is "to charge", or "not to charge" for the custom apps. Both sides have valid arguments, but here is a third option. Do both.
Release the full version (after bugs have been squashed) and charge for it - pricing structure TBD. There will definitely be demand for the apps. Maybe do some giveaways to increase publicity.
After an amount of time (again, TBD), make the apps free to anyone. This would be another boon to the community and good publicity.
Why not make a requirement for a balance of ??key to use app.
additionally have requirements for each additional trading symbol you have a btn to purchase/unlock that symbol and will add to your key balance and unlock trading features for each additional currency?
That way you can pick and choose which coins you want to use the app with.
key... unlocks.. . other currencies... you see what i did there?