Since the 2.0 release, Guile’s architecture supports compiling any language to its core virtual machine bytecode, and Scheme is just one of the supported languages. Other supported languages are Emacs Lisp, ECMAScript (commonly known as Javascript) and Brainfuck, and work is under discussion for Lua, Ruby and Python.
This means that users can program applications which use Guile in the language of their choice, rather than having the tastes of the application’s author imposed on them.