The 2 reasons we also include eGo in the name description is
1: list that it is compatiable with all eGo parts
2: for search engine optimization (so the product can be found when searched for)
This style PV was originally created by Joyetech hence the Joye eGo. From what I understand an engineer that worked at Joyetech that helped design eGo quit Joyetech and is now with Eastmall/Unicig and they developed the RiVa which has a soft rubber button versus the plastic type button on the eGo. The RiVa (750 mAh) also has 100 more mAh than the Joye eGo (650 mAh) The newest model RiVas (which we carry) are also a True 3.7V device where as the Joye eGo is only about a 3.2V device. See below links about voltages:
Titanium Riva Riva Starter Kit
Battery Voltages -- Surprise!
Last but not least, the RiVa is also being produced by other companies like Hello, and I would classify these as a knock off RiVas. With all the above distinctions, I really wouldn't classify the RiVa as a knockoff eGo with the RiVa being a better PV compared to the eGo.