Hi Jason, Scott,
I'll tackle your questions one at a time.
1. A one button game is, generally, a game that has only one button input.
These kinds of games are often available on mobile phones to allow simple one handed gameplay, and they are also games which have been designed with the idea that it be accessible to all -- including players who are physically or developmentally disabled.
There are a lot of good resources of information for this style of game online, including
OneSwitch.org.uk, but the general idea is that input be as simple as possible - using only one form of input. So, for example, a great example of a one button game is [url=http://www.starquail.com/Games/]Sky Puppy[/a]. The style of this game could easily be recreated in Dr. Dobbs - pushing or holding only one button allows you move Sky Puppy around the levels.
Dr. Dobbs, as it currently stands, is not an accessible game, for example. You have several buttons to hit (often at the same time) which is beyond the abilities of many users!
We generally expect the one button category to only feature games that use one button, but if games are created that use, for example, only mouse movement, or on the Windows Mobile version, only stylus input, even, we'd be very interested!
2. The contest is available to people all across the world. When we say "state" we really mean state/province/county/etc.! So don't worry about it.
Thanks,
Mathew Kumar
Community Manager