Looks like they will have an API.
From the campaign description;
Weather enthusiasts will appreciate the ability to export station data into 3rd party tools and developers will love how easy our forthcoming API allows data to be used in their applications.
Backer question/feature request; Open API: Hope very much the team is working on this. As doing so will ensure quick adoption, sales growth, and market adoption.
Creator's answer; Yes, absolutely - the API is being developed in parallel with the hardware.