As Keith has written elsewhere:
Do make sure you check out the licence agreement, which stresses that you are allowed to install multiple copies of Scrivener for your own use. So you don't have to pay more than once to install it on all of your computers. Even if you have 10 computers, you are welcome to install Scrivener on all from one licence, provided they are all your computers - or your family's (under the same roof).
I don't want you to pay twice when you don't need to!