You are buying a licence to use the builder's product on the terms they set. Guiru records your entitlement and tells the product you are allowed in. Guiru does not become the software's author or its support desk.
The product page states where the transaction happens: Buy with Guiru, included with Member, free, an external store, or an affiliate link. If it is not us, we say so before you leave.
Your purchase appears in Purchases with a receipt, and the product appears in your Library. Access is granted immediately; if it does not arrive, the receipt page shows the state of the payment and the entitlement.
Refunds: see the Refund Policy. Broken, deceptive or unsafe products: use the report form. Reports are read by people, and a product that no longer works can be suspended or removed.