Customisation to avert SMS looping


We want to use SMSSync to facilitate citizen feedback for a rural development programme in a small developing country. The older version 2.0.1 beta works well. We want to use auto reply but don’t want to use keywords if possible to make it as simple as possible. However, when the network operator sends a short code or broadcast SMS this sometimes leads to looping with autoreplies triggering autoreplies etc. With Android Kitkat you can’t block incoming SMS from reaching running apps that are listening for them, at least I have tried but not found an app that will do it. Of course we could just use a device running an earlier version. But I wondered if we could tweak the app so that it does not reply to short code numbers. I have some very beginner level Android skills using Eclipse. I note one can decompile and modify any APK but not sure about the ethics of that.Basically only a tiny edit with 2 lines of code in one of the utils processes will do the job. What is the best way to go about this? Is the source code available so it loads into Android Studio 2 as a new project and will compile again, legally/ethically? Thanks!