Hi hafool. The weapon in the picture you quoted looks like one of a number of patterns of bayonet designed to fit the AK47 assault rifle, this one being a standard bayonet pattern. The Chinese version of the AK47, the Type 56, normally had a folding bayonet built in to the underside of the barrel, although there were exceptions. There is a strong possibility that the bayonet shown is a copy, but it should fit onto the muzzle/boss of the AK, or the Chinese Type 56 without the folding bayonet.
I don't know what the laws regarding such weapons are like where you live, but beware, this is a lethal weapon, designed for one purpose only!