Need someone to get me a motor off ebay

I haven't had a look inside the Leopard motor but a friend bought a 4074-2150kv for his Hyper7 and seeing it run seems like a good motor. Must be reasonably efficient because it stays pretty cool and power is similar to my CC 1515-2200kv.

Now I don't want to start anything but what exactly makes them a clone? Fact that they are 4 pole motor? Fact that they look similar? I am confused. How different can you make one motor look from another?

Not defending anyone but just trying to wrap my head around it. Also what brian015 said makes a lot of sense. Why is Castle allowing their US dealers to sell the Leopard motor side by side next to their product? If Castle felt so strongly that Leopard motors are a clone surely they would have put a stop to it.