This is mainly a Mac promo deal, but it works on PC downloads too.
And it's not just for Scrivener, it's for all software (note not games, as noted by an Amazon rep on MacRumors) downloads. I just thought Scrivener is pretty relevant over here since we're readers and writers.

I myself "bought" Chronicle for bill reminders and didn't pay anything since I had the code.
Some other decent stuff in there too.
The coupon code is
MACR0913 and you want to start here:
http://amazon.com/macsoftware
If you're not using a Mac, you can also go here:
http://amazon.com/digitalsoftware
It's only for one use, so you can't like buy multiple $14 dollar apps. But you CAN buy a $4 and $5 group of apps and it'll leave you a few dollars leftover to buy another one to apply the remaining amount to.
Oh and, you get an Amazon downloader, but otherwise the apps aren't linked to the server, it's like downloading from the publisher itself and gives you a standalone download you can backup. My download was version 4, and I was able to upgrade to 5 easily.