It is a very strange article, which, when talking about R, omits to mention its direct-source origins in the S language (later on, the S-plus language, and now S4). R is much more like S than SAS or SPSS, and many statisticians preferred to use it, even though it cost a lot of money, than use SPSS or even SAS (I think SPSS was viewed as the most inferior one amongst those mentioned.) As I said, this was the view amongst statisticians, which are a different group to those who just use statistical packages. I think its a serious omission in this article.
http://en.wikipedia.org/wiki/S_%28programming_language%29 although wikipedia gives a short summary, not so outrageously wrong, and it refers to a useful history in the form of a pdf document about it.