If you are developing software for iOS with b4i, you will need a windows operating system. If you are using an m series macbook, you need to purchase extra software such as parallels. Of course, we need to have a windows license. If everything that b4i needs is already on macos, why does it only have windows version?
Because all the B4X IDEs share a huge amount of common code for editing, parsing and generating B4X code so it does not make sense to replicate that in a mac environment as it would double the maintenance and upgrade effort needed.
Everything written above is true. The IDE is a .Net WPF application. It is also based on several "heavy" WPF libraries. WPF is Windows only and the .Net cross platform UI framework is too limited.
To use B4x on a Mac Computer you need to install Parallels. The good news is that B4x is running also on M1 MAC and Windows Arm/64. While it works like a charm it is the best solution using basic Language. That it is Windows only is not the big deal using Parallels.