For me, it was reverse engineered. I am not an expert or even conversant in decompiling Android APKs. It took the decompiled Java (app was apparently written in Kotlin) and extracted all the necessary information.

Call it what you will, the point is I do not have the necessary skills to accomplish this task, but I was able to go from an APK to a working implementation that was controlling the lights in my RV in a couple of hours back in early April using whatever was the current version of Opus at the time. While I understand what it did to accomplish this, it might as well be magic for me, because it would take me months of free time to get to where it got.

It also wrote out documentation of the protocol so subsequent work would not require reading decompiled Java code.