Amazon KDPhttps://kdp.amazon.comSelf-publishing rail. GitHub Sponsorshttps://github.com/sponsorsOSS funding. Gumroadhttps://gumroad.comDigital product storefront + API. Ko-fihttps://ko-fi.comTips + shop + memberships. Lemon Squeezyhttps://lemonsqueezy.comMerchant-of-record for digital products. Open Collectivehttps://opencollective.comTransparent project funding. PayNowhttps://paynow.co.zwZimbabwe payment gateway. PayPalhttps://developer.paypal.comPayments + payouts API. Stripehttps://stripe.comPayments infrastructure. T3rnel WavePayhttps://github.com/t3ratech/t3rnelPayment authority (sibling product; PayNow-first). x402https://x402.orgHTTP-native micropayment protocol for agents.