Does it work? If so, don't worry about it.
"Real" Joye eGo batteries are voltage regulated to 3.4 volts while many of the others (Riva, KGO, etc.) are not so they come off the charger at 4.2 volts and drain down from there. I use KGOs myself and my son has Rivas and they've been working fine for months. To me, a "knock-off" is a cheap imitation that doesn't work, not just a competing product from a different manufacturer. As far as vendors, stay with the ECF registered vendors and you'll be fine. I've used nearly a dozen different vendors so far and got good service from all...