Apply coupon from an affiliate link to ubercart
Try ECO (Extra Customization Options for Ubercart).


  ECO (Extra Customization Options for Ubercart) provides additional ("extra") options to customize Ubercart.
  
  Some of the functionality provided also includes a degree of integration with other contributed modules like Legal, Webform, and Ubercart Discount Coupons. Among the customization options are using URL parameters to auto-apply coupons in checkout, requiring new customers to choose a password, and integration with the Webform module to pre-populate address fields in checkout.