Things to remember if you're downloading the source to run it yourself:

1. Your domain must be registered with Google, https://www.google.com/accounts/ManageDomains
2. After you have verified your domain, you'll get your OAuth secret.
3. The OAuth secret must be set as the environment variable OAUTH_CONSUMER_SECRET=<my_secret> in your runtime environment.
4. The OAuth goodness wil only run on the domain that is registered with google (not localhost)

For further information, see http://open.bekk.no/2009/12/18/gmail-and-google-calendar-with-openid-and-oauth/