can't install R on a G5...

Define "this stuff" ;). The GUI is simply the icon you see, so you "uninstall" it by moving it to Trash. This is true for almost all Mac apps.

I was meaning the gfortran-4.2.3 and tcltk-8.5.5-x11 "stuff" you wrote 
it's useless unless I "want to install packages from sources that 
contain Fortran code", something I'm pretty sure I'll never do ;-)
Back to my question: there's a way to delete "this stuff, without using 
AppDelete :-P or I just forget them and let them occupy a tiny bit of my hd?

thanks
have a nice day
Finrod