Getting custom record list in scriptable template?

I'm trying to retrieve a list of custom records in a scriptable template that will be sent from an invoice.  I've referenced this SuiteAnswers article below, but I still can't get it right.  I have a custom record where the field custrecord_ntnx_lic_tran_num refers to a transaction list field on the custom record where record is parent is checked.  The custom record id is customrecord_ntnx_license

Here's my template content:
[PHP]<#list transaction.custrecord_ntnx_lic_tran_num as sublistLicense>
  ${sublistLicense.custrecord_ntnx_lic_sku},${sublistLicense.custrecord_ntnx_lic_start_date} </#list>[/PHP]