Google checkout for Miva Merchant 4 is NOT owned or provided by Miva Merchant. Only Google Checkout for Miva Merchant 5 is owned and provided by Miva Merchant.
We did not provide the instructions for installing on Miva Merchant 4 with OpenUI. Google did, in cooperation with one of our partners Sebenza Studios (please see: http://www.sebenza.com/googlecheckout.html). For any assistance for MIVA Merchant 4 / Google Checkout users group sponsored by Google, Please visit the following: http://groups-beta.google.com/group/google-checkout-for-miva-merchant/
The Google Checkout module for Miva Merchant 4 requires the MivaVM 5.06 or higher be installed in your store. Please contact your web host for assistance with this if your engine is an older version and you are installing the Google Checkout module.