Custom jQuery validation error messages
This looks fine to me.

I only have 2 minor points:


You could assign the .text() once in the var statements so that your string concats look like customMessages.email = "'" + label + "' has an invalid email address."; This way you are not repeating text() all over the place.
var customMessages = [{}]; looks odd, because you are afterwards assigning straight to the array instead of the empty object. Simply replacing that with var customMessages = {};  works in the fiddle.