That's because the /RPC2 interface was for the old version 0.3 of Browsershots which moved to http://v03.browsershots.org/ for historic reference.
32.
Recent Screenshots
33.
This saves your time to get screenshots and help us pay off some development and hosting cost.
34.
Your screenshots are private (only you will see them, or somebody who already knows your URL).
35.
Your PayPal email address is %(paypal_email)s (same as for your Browsershots account).
36.
Contribute by running screenshot factories for us
37.
The current version 0.4 uses http://api.browsershots.org/xmlrpc/ for the screenshot factory API. You should install a package with "0.4" in the name, or check out the trunk from Subversion.