There are 4 development tools based on the B4X programming language:
B4A - Android apps.
B4i - iOS apps.
B4J - Windows, Mac, Linux and Raspberry Pi apps. UI, console and server. Based on Java / JavaFX.
B4R - Arduino / ESP8266 / ESP32 programs.
The repo is organized into 4 folders and another B4X folder for cross platform resources - resources relevant to B4A, B4i and B4J.
libraries_mapping.json is an index of b4xlib libraries. It lists all libraries (only b4xlibs for now), with links and descriptions.