The link you link to for getting an API key says:
Sign-up for an API Key
The Google Loader no longer requires keys. You don't need to make any changes if you're already using one, but if you choose you may simply remove the key parameter from your requests. Remember that some API calls still require proper identification through HTTP referer as per the documentation and Terms of Service.
Note that some APIs use other keys (e.g., from the Google APIs Console) which are unaffected by this change.
Last updated February 2, 2012.