You can remove the requirements to login completely but the records that are created as a result will not be able to be associated with a user.
To remove the login requirements you will need to work on the checkout, confirm and pp_confirm page. What you will need to do is remove the validations for the password. You will need to remove the server validations as well as the spry validations for this.
On the checkout page you will need to remove the spry validations, these are controlled with these lines of code:
var sprypassword1 = new Spry.Widget.ValidationPassword("sprypassword1", {validateOn:["blur"], minAlphaChars:1, minNumbers:1, minChars:6});
var spryconfirm1 = new Spry.Widget.ValidationConfirm("spryconfirm1", "UserPassword2", {validateOn:["blur"]});
Next on the confirm page you will need to remove the server validations. Here is the code to remove for the server validations:
$WAFV_Errors .= WAValidateRX(((isset($_POST["UserPassword"]))?$_POST["UserPassword"]:"") . "","/[a-z,A-Z]/",true,5);
$WAFV_Errors .= WAValidateLE(((isset($_POST["UserPassword"]))?$_POST["UserPassword"]:"") . "",((isset($_POST["UserPassword2"]))?$_POST["UserPassword2"]:"") . "",false,6);
Finally on the pp_confirm page you will need to remove both spry and server side validations. Here is the spry to remove from the pp_confirm page:
var sprypassword1 = new Spry.Widget.ValidationPassword("sprypassword1", {validateOn:["blur"], minAlphaChars:1, minNumbers:1, minChars:6});
var spryconfirm1 = new Spry.Widget.ValidationConfirm("spryconfirm1", "UserPassword2", {validateOn:["blur"]});
Here is the code to remove for the server validations:
$WAFV_Errors .= WAValidateEL(((isset($_POST["UserPassword"]))?$_POST["UserPassword"]:"") . "",6,50,true,3);
$WAFV_Errors .= WAValidateRX(((isset($_POST["UserPassword"]))?$_POST["UserPassword"]:"") . "","/[0-9]/",true,4);
$WAFV_Errors .= WAValidateRX(((isset($_POST["UserPassword"]))?$_POST["UserPassword"]:"") . "","/[a-z,A-Z]/",true,5);
$WAFV_Errors .= WAValidateLE(((isset($_POST["UserPassword"]))?$_POST["UserPassword"]:"") . "",((isset($_POST["UserPassword2"]))?$_POST["UserPassword2"]:"") . "",false,6);
This will allow a user to go through the checkout without logging in or creating a new user.