RPN Calculator (Reverse Polish Notation) for Android.
This is the only good RPN calculator app I found.
https://github.com/evolquez/rpn-calculatorOpen linkView original on sh.itjust.workshttps://github.com/evolquez/rpn-calculatorOpen linkView original on sh.itjust.works
Not exactly the answer you're looking for, but here's some info about Reverse Polish Notation...
https://en.wikipedia.org/wiki/Reverse_Polish_notation
Just use some HP calculator emulator. That way you don't have just an RPN calculator, but a full fat graphing calculator.
I've been using Droid48 forever. It's perfect.
https://play.google.com/store/apps/details?id=org.ab.x48
https://github.com/shagr4th/droid48
I'm using this one and am very happy with it.
It has not been updated since a year.
What has changed about RPN or calculators in the past year?
Android had changed.
It works as well as on the first day I started using it, so I don't really mind.
Realcalc has an excellent RPN mode (enabled through Calculator Type in Settings). I've used it for the last six years or so (technically, in the premium version of the app).
Edit: Not open source - sorry, didn't see the community!