Code is a weird one because there are times when it's correct (e.g. "encryption codes"). But when it's used to mean "software" it should never be "codes", IMHO, though I guess there's a minority in disagreement.
[0] http://people.sc.fsu.edu/~jburkardt/f_src/f_src.html
[1] http://www.unige.ch/~hairer/software.html
[2] http://www.mcs.anl.gov/project/openadf-automatic-differentia...