There's nothing illegal about what they are doing as far as I can tell. You don't have to maintain certifications to sell filters. It's like UL in electronics...quite optional and up to the buyer to insist on certain things.
I would think falsifying an EPA ID number and publishing the document (in this case basically to sell their product) would be illegal. "Uttering" comes to mind. In that case, I don't know how they'd keep getting away with it after all these years.
I understand that GAC wouldn't be a solution for hard water. In the case of Berkey, I'll say that *supposedly* it does remove heavy metals.The water treatment provided by a GAC system like the Berkey is not the same as that of RO. GAC works on the basis of adsorption while RO relies on osmosis (transfer though a semi-permeable membrane). While GAC is good at removing contaminants like chlorine or organic compounds its not good at removing metals or dissolved solids like salts and other minerals like calcium and magnesium (i.e., hardness).