ok for starters copyright is not for books, its for
intellectual property. so the device itself will be patented but the idea is copyrighted. hence you can't use someone else's idea to make money
secondly when you say modify the USB size but not its layout then you might need to receive rights from whoever designed it.
may I be so bold as to why you want to change the size? its just a weird thing to do when USB connectors come in so many different sizes already.
Apple have that nasty connector that looks like they decided to add more pins. USB itself has 3 (I know someone is going to correct me here) +5, gnd and data. next is current and in all reality if you need more than about 2amps (that's what most chargers are rated) then getting a specialised chord (DC jacks style) might be better.
if its because soldering those little connectors is hard then buy a few hundred from a PCB place, it'll cost a little extra but for prototyping when you can't older that little pin makes it worth while.
if you are adding more wires then USB isn't the best...
this long winded reply is just because I am curious as to the application and reasoning for a new type of plug
below are some pics of already available plugs. these are not to scale. the second top left hand is commonly found on printers and pretty big