Open source software in scientific computation

The purpose of this presentation is to establish that, in the domain of Scientific Computation, using Open Source Software can be very useful. At first it will be pointed out that there are generally accepted ideas in the domain of Open Source Software which do not always reflect reality. Then the economic model for Open Source Software is addressed: is it possible to make money with it and how? In particular, we show that both closed source commercial software and free Open Source Software can coexist together. The problem of licenses and the ways to put software as Open Source is also addressed, in particular how to transfer software issued from research to professional software. As an illustration of the previous points, the evolution and strategy of free Scilab software is described.