Gtk-Stream is described as 'Tool that takes on its standard input a XML description of what your application should do (spawn a window, add/remove a widget, change a property, add a stylesheet, ...), while outputting events on its standard output' and is a Shell in the os & utilities category. There are nine alternatives to Gtk-Stream for Linux, Mac and Windows. The best Gtk-Stream alternative is Zenity, which is both free and Open Source. Other great apps like Gtk-Stream are Yad, wxFormBuilder, easybashgui and KDialog.