One way to mount the Mathematica .iso is to create /media/iso and add the following line to the fstab:
/<location/of/mathematica.iso> /media/iso iso9660 exec,ro,user,noauto,loop=/dev/loop0 0 0
Now you can mount it with:
Running the Installer
You can start the installer by navigating to:
Run ./MathInstaller with:
Add the directories containing Type1 and BDF fonts to your FontPath.
If you have font rendering problems where certain symbols don't show up (i.e. "/" appears as a square), try uninstalling the package "mathematica-fonts".