Auth Net includes SSL encryption. Why does Ushop need to be on a secure server? Isn't the SSL encryption with Auth Net enought to meet the requirements?
At this time, if you are using uShop's built-in interface to Authorize.Net, then No, you don't need to have uShop installed on a secure server. This is because all of the sensitive payment information is collected on Authorize.Net's secure server and only the accept/decline response is sent back to uShop.