To upgrade to v5 of our Reseller APIs, go to your Developer Console, and create an app to get an API key for v5 endpoints.
You can still use v4 endpoints after you get your v5 API key. You can transition to v5 on an endpoint-by-endpoint basis, or you can begin using v5 endpoints exclusively at any point.
Please note, however, that your v5 API key cannot be used to send requests to v4 endpoints, and vice versa. Also, there are differences between the versions' requests and responses; attempts to upgrade by replacing "v4" with "v5" in your requests will cause your integration to fail.
For Vendors, there is currently only v1 available.