Rebilly offers a Javascript SDK and a PHP SDK to help interact with the API. However, no SDK is required to use the API.
Rebilly also offers FramePay, a client-side iFrame-based solution to help create payment tokens while minimizing PCI DSS compliance burdens and maximizing the customizability. FramePay is interacting with the payment tokens creation operation.
Installation and usage instructions can be found here. SDK code examples are included in these docs.