You can clone with
HTTPS or Subversion.
After visiting the link provided by "bundle exec ruby oauth" dropbox says: "Only a limited set of users can receive access tokens while this app is in development mode"
I enabled the "additional users" option on the dropbox app options. I also applied for production status so anyone can use this app but I'm not sure they'll approve this since the keys are in plaintext.
I believe it should be working for you right now but in case it doesn't you can create your own app in https://www2.dropbox.com/developers/apps and replace the tokens in lib/initializer.rb
Sorry about that but I believe you're the first person other than me trying this out :)
No problem, I too have felt this pain before :)