S is programming language that started as a research project at Bell Labs used for statistics and statistical graphics. The language was developed for data analysis, statistical modeling, recreation and graphics. S has a general-purpose language whereas S-Plus and R, are implementations of S. R is built on the same foundation as S as well as executed with the same functions. Most statistical functions programmed for S run under R and vice-versa. R operates the way a problem is worked out as it is more flexible.
The differences between S and R, are that the standard data files are not compatible although data can be transferred easily. Graphical output is different as the products use different engines and programming model. With interaction of R, interfacing to other software especially databases are entirely different than in S.
The free and open-source software movement (FOSS) is a movement which supports the usage of open source licenses for some or all software’s hence you have access to the software for free. This allows a larger view for open collaborations. The free and open source movement had originally started to spread the concept of non-profit collaborations. This allows programmers to contribute to open source communities by voluntarily writing and sharing programming code for software development. The FOSS allows anyone to obtain and modify open source code for free. R is available as free software under the terms of the Free Software Foundation’s GNU General Public License.