There never was a Smart App as this was designed to be as simple as possible and it simply wasn’t needed. All of the work is done by the Device Handler, sending signals directly to the Arduino.
As far as maintaining the code and implementing improvements, there honestly hasn’t been a need, I’ve been using this on some windows for these four years and it’s been rock solid.
This project did somewhat lead to a much more robust creation by @blebson with his genius use of moteinos that could be perpetually powered by solar panels.
Honestly, I would recommend his version to anyone going to DIY smart blinds on SmartThings today. I have a few windows that have been going for over 2 years with his version, purely solar powered, haven’t needed a battery change or manual charge, and with a daily open and close scheduled.