This page walks you through the process of creating a Google account with your non-Google email address. Doing so will enable you to access the OSDC-internal site using the email account listed with the center.
First, go to http://accounts.google.com/newaccount and fill in the information requested. Fill in your email address (1), choose a password (2 and 3), your birthday (4) for age verification, and type the obfuscated word displayed at the bottom of the page (5). When all the fields have been filled in, submit that information (6).
Once you submit that form, you'll be met by a screen like this:
As mentioned, Google has at this point sent you an email to confirm that you are the owner of the email address in question. Check your inbox for this confirmation email; it should resemble the one below. You should then click the link indicated:
Clicking that link should result in a web page like the following:
You can then navigate back to the account creation page that was active prior to switching to your email to confirm your email address. On it, click the "Google Accounts homepage" link indicated below.
You'll see a page like the one below. Enter the password you used to create the account, and click "Sign In".
At this point you'll be logged into Google using your non-Google email address, and provided it is the one the center has on its records for you, you should be able to access the internal documents and website!