Yes, if payments are being submitted through GRIN, then in order for your payments to be processed you must submit a W-9 or a W-8BEN for non-U.S. individuals. Both a PayPal email and a W-9, or W-8BEN, will be required in order for any payments submitted to you to be processed.
We understand that there may be concerns about providing some information, such as a Social Security Number, however, we can assure that all information provided on the tax form is kept confidential. If you do not wish to provide your SSN you do have the option of providing a Tax Identification Number (TIN) instead. However, at least one will be required in order to complete the tax form.