In January 2020 we launched our v2 API, documentation is here - https://api.bookwhen.com/v2
You can create an API access token here on any Bookwhen account.
Currently, the API includes calls for event information, but we plan on making bookings data available in the future too.
Version 1 (deprecated)
Our V1 API documentation can be found here. v1 is now deprecated, but if you do require an API access key for your account then please email firstname.lastname@example.org with your account link.