Yes, in some traditional Fortran environments "codes" has been used where in other environments one would have said "libraries" or "programs", e.g. "these are some codes for solving systems of ordinary differential equations" or "this is a code for solving boundary elements problems".
So in this sense, as a synonym for a library or a program that accomplishes some function, "code" is countable.
It’s not, but it’s somewhat common among people making numerical models of dynamic systems and that sort of thing. People like Steve Brunton will often say all the “codes” are available to go along with his videos for example https://youtube.com/@eigensteve?si=IVLparAOZ9XDauTz
I think "codes" is peculiar to what is now called HPC, where it's been common since at least the 70's. It's not specific to Fortran; there are C/C++ HPC codes too.
So in this sense, as a synonym for a library or a program that accomplishes some function, "code" is countable.