BCX is called "The BASIC To C Translator". This means that BASIC code is converted to C. After that the resulting C code is compiled with the devKitPro toolchain with all the libraries like a normal Wiibrew application.

You have to have a bit of C knowledge to use BCX since you sometimes have to inspect the resulting C code.

BCX has been developed by Kevin Diggins BCX for Windows

The package for download here describes how to use it for WII development.