I'm curious about this as well. I've been researching on the forums and found two answers: Either change the key in plugin.xml or change every instance of the plugin name throughout the file.
I gave the first suggestion a go and it resulted in a 500 error. I had to manually un-install the plugin to get my site to work again. The two plugins I was attempting to duplicate were the Virtual Gifts and Groups plugins.
I haven't tried the second option yet but wanted to check with others to see whether this is the right way to do it, or I'm going down the wrong rabbit hole. Any advice?