The Dropbox authentication screen says: "This app will create a folder named webcache in your Dropbox. The app will only have access to this folder." But yeah you have no idea what's going to happen when you click that grey Submit button.
I agree the lack of polish makes it look spammy. Maybe some rounded corners and bubbly clouds would make it more trust-worthy. Along with an invitation to come over my house and have a beer.
I don't want to give you a subdomain! How about "Enter the subdomain name you want:". Or something.
i'm also seeing lots of errors in the server due to authentication reasons, clearly i have some learning to do in terms of how oauth actually works.