Yes most of this can be done, though if I were you I would just use openSUSE KDE as opposed to the gnome edition as gnome classic doesnt work the same as it used to, you are better off with MATE or something if you like the old gnome interface.
in any case:
Gambas can be installed here
http://software.opensuse.org/package/gambas3
scalib:
http://software.opensuse.org/package/scilab
gscanpdf (guessing you made a typo)
http://software.opensuse.org/package/gscan2pdf
the only one I dont find a opensuse repo for is onboard.
In any case opensuse has community repositories (much like Ubuntu and debian) and all are pretty much good to use.