I think everybody is missing the point here. The developer said he is "based out of US". Shouldn't he be able to avoid paying the withholding tax thanks to the W-8 BEN-E (W-8 BEN or W-8 IMY) IRS forms? Furthermore SaaS and Software is only taxable in certain states and not in others: https://www.taxjar.com/blog/saas/saas-sales-tax
Laura