A general question: Is language S a component part of R?

In the "Introduction and preliminaries" the "An Introduction to R" manual
says about R: "... Among other things it has ... a well developed, simple
and effective programming language (Called 'S') ... ". Now I'm a little
confused. This means that language S is a component part of R? And S is not
free? But R is free? Or the mentioned S is only "a free implementation" of
the "true S"? Can anybody explain this? I want to know.

Thank you!

'S' is a language, invented at Bell Labs
(http://en.wikipedia.org/wiki/S_(programming_language)) which has two
major implementations. S-Plus, which is a commercial product, and R,
which you know well.

R was originally quite like S/S-Plus, but it's changed over time and
diverged aways and now I believe the R README says R is 'not unlike'
S.

Consider, e.g., Python, which is a language (specified in
documentation) with multiple implementations: CPython, PyPy, Jython,
IronPython, etc. If R and S-Plus had identical functionality they
would be different concrete realizations of the abstract 'S' language,
but they're more than slightly different in practice.

Not sure if that helps at all....

Michael