Module is not supported anymore.
Check out Google Checkout code from Google http://code.google.com/p/google-checkout-oscommerce/

 

MagneticOne osCommerce Google Checkout module advanced features: Support for Product Attributes Module supports product attributes with price modifications (like "Size XXL +$10"). Support for Taxes All standart tax modules are supported "out of the box"! Support for Custom Tax Modules Supports Tax Modules, created according to osCommerce requirements Support for Shipping All standart shipping methods are supported "out of the box"! Support for Custom Shipping Methods Supports Shipping Methods, created according to osCommerce requirements Extended Logging Very usefull to see how your store visitors using this payment method Test mode support Enables you to test prior to enabling this payment method Supports Google Analytics integration Google Analytics enables a merchant to understand how visitors interact with the merchant's website. Google Analytics also helps the merchant to identify navigational components that promote or inhibit conversions to sales, enabling the merchant to optimize ad campaigns and website content for increased sales. Google Checkout merchants can use Google Analytics to track buyers who leave their sites to complete the checkout process using Google Checkout. Google Checkout - Google Analytics official blog And more... After installing you receive Google Checkout button under your store checkout button, along with all the server side features Google Checkout offers.

I Do Recommend This Contribution: Magneticone's osCommerce Application was a lifesaver for my Website. Their Integration was one of the most easily applied scripts that I have ever Integrated on my website with simple easy to follow directions. I was very happy with the support they gave me to get it up and running, as the only problems I had on my install was some things that I had overlooked while installing. This is an awesome program and it Integrated Google Checkout on my site and looks good too! Check it out at my Website and see for yourself:  www.ComputersDirectUSA.com  It will be the Best Money You Ever Spent to Make More Money ! Dan Abner  (Owner)  www.ComputersDirectUSA.com

osCommerce Google Checkout Level 2 payment module is designed to be used with osCommerce and Google Checkout Payment system.
This is COMPLETE Google Checkout Level 2 integration.

We HIGHLY RECOMMEND you to add this payment method to your store, it is very popular now.
Customers love Google - they will love your store!

This package contains all files needed plus an updated readme file with installation notes. This module uses Google Checkout API.

Live store examples

http://www.allthehotkicks.com
http://www.computersdirectusa.com

How module is working

Module is passing shipping costs to Google Checkout, product attributes price is included in products price. Taxes are also passed to Google Checkout(i.e. supported).

Check technical details of Google Checkout Level 2