Interestingly, nothing else seems to be wrong (at least I didn't spot anything else). And it's not even consistent, eg: crofs (instead of cross, so only one 's' became 'f' here).
More expensive OCR software tends to get around this by using probability models to guess the correct word (i.e. "best" is much more likely than "beft"), but I'm guessing they're using some mid-range OCR package.
They are reproductions of the originals, and maintain the original fonts and orthography. This includes the long s, as well as certain ligatures (like ct), and has absolutely nothing to do with their choice of OCR software. In fact, there's no indication that OCR software was used at all.