The installation of the SciLab GetFEM++ toolbox can be somewhat tricky, since it combines a C++ compiler, libraries and SciLab interaction. In case of troubles with a non-GNU compiler, gcc/g++ (>= 4.8) should be a safe solution. The minimal SciLab release is the 5.2.2.
See the download and install page for the installation of GetFEM++ on different plateforms.