Hi Piotr, "If you make a Python/PyQt4 application then on OSX it won't need X server" True, but from what I've understood so far, based on: http://qtocc.wiki.sourceforge.net/opencascade_osx "At the moment, it seems to be impossible to use OpenCASCADE outside of the X11 system." Which suggests that I need the QT4-X11 version, right? Thanks, -jelle