Hello,
The fields are required however they can be hidden by editing the /templates/orderforms/your_active_template/configureproduct.tpl file.
https://github.com/WHMCS/orderforms-standard_cart/blob/master/configureproduct.tpl#L120-L148
To remove one or more of the default fields on your order form entirely, you can change the field type to hidden and supply a unique value.
For example:
Find:
<label for="inputNs1prefix">{$LANG.serverns1prefix}</label>
<input type="text" name="ns1prefix" class="form-control" id="inputNs1prefix" value="{$server.ns1prefix}" placeholder="ns1">
<label for="inputNs2prefix">{$LANG.serverns2prefix}</label>
<input type="text" name="ns2prefix" class="form-control" id="inputNs2prefix" value="{$server.ns2prefix}" placeholder="ns2">
Replace with:
<!-- <label for="inputNs1prefix">{$LANG.serverns1prefix}</label> -->
<input type="hidden" name="ns1prefix" class="form-control" id="inputNs1prefix" value="host{$smarty.now}" placeholder="ns1">
<!-- <label for="inputNs2prefix">{$LANG.serverns2prefix}</label> -->
<input type="hidden" name="ns2prefix" class="form-control" id="inputNs2prefix" value="host{$smarty.now}" placeholder="ns2">
The password field is expecting user input and if not required you can hide this as above.
We recommend creating your own custom order form to preserve changes through any upgrades - http://docs.whmcs.com/Order_Form_Templates#Creating_a_Custom_Order_Form_Template