Cython is a compiled language that generates CPython extension modules. These extension modules can then be loaded and used by regular Python code using the import statement. Cython is written in Python and works on Windows, Linux, and Mac OS X, producing source files compatible with CPython 2.4 through 3.3.
It works by producing a standard Python module. The difference from standard Python behavior however, is that the original code of the module is actually written in Python but is then translated into C. The resulting code is not completely independent, although it is fast, but rather makes many calls into the CPython interpreter and CPython standard libraries to preform actual work. This saved considerably on Cython's development time but requires a dependency on the Python interpreter and standard library for the module.
Despite the fact that most of the code is being output in C. At least a small stub loader written in interpreted Python is usually required (unless you want to create a loader in C, working with messy undocumented internals of CPython), but this is not a major problem due to the dependency on the Python interpreter.