R is a language which is not entirely unlike the S language developed
at AT&T Bell Laboratories by Rick Becker, John Chambers and Allan
Wilks.

R is free software distributed under a GNU-style copyleft.

This port has  most of the functionality in the first S book (the
"Blue Book") and many of the applications.  In addition, a certain
amount of functionality from the second S book (the "White Book")
has been implemented.  In particular functioning versions of "lm"
and "glm" and their associated "summary" and "anova" methods  are
provided.

WWW: http://stat.auckland.ac.nz/r/r.html
     http://stat.ethz.ch/R/manual/