Puppy 4.x series do not include fortran in the dev_4xx.sfs official files.
I have compiled gfortran-4.2.2 and make it available in two forms.

1. dev_410_with_fortran.sfs is a replacement for the official dev_410.sfs for puppy 4.1 
which includes gfortran

2. gfortran-4.2.2.pet is a pet-package for those who prefer to use the official dev_410.sfs
file and willing to add fortran as a pet install. Notice that in order to use gfortran, 
the dev_410.sfs should be active!