I've been looking for the best language for scientific programming...I'm looking for open source....I've seen in several articles that on scientific computing, Python is steadily eating other languages’ lunch...but the doubt still remains.
Have you heard about the Julia language i can't really tell you if it is free or not but is a high-level, high-performance dynamic programming language for technical computing, with syntax that is familiar to users of other technical computing environments...it is widely compare to other languages that can or could be used for numerical and scientific computing like : C, Fortran, Python, Matlab/Octave, R, JavaScript, Java, Lua, Go, and Mathematica.
Depending on professional background (or simply your taste) you may choose among Python, R or Julia. The below links provide interesting comparisons among these languages, taking different aspects into account: