In the retail world, "sell by date" is very different from "date of expiration". With that said. Coffee is a fruit. It is perishable, even after it is roasted and can grow mold. Additionally, if you are using a standard brewer, the brewer itself can be susceptible to mold caused by water condensing inside the machine. Unless the coffee has been stored improperly until today (stored in a moist environment with light, exposure to elements, etc.) I would think it would be okay to drink. Coffee is all about taste; to another person, old coffee will taste flat and not have such an aromatic flavor as freshly ground coffee.
If there is visible mold on the coffee, I would not drink/grind it. The best thing to do is always consult your doctor before doing anything.