Public Endpoints
Since Gemini is first and foremost facilitating a public festival, it is only natural that there would be a certain amount of event information that is freely available to the public. As such, there are several endpoints that do not require authentication to use. There are rate limits in effect to prevent abuse of these endpoints, but aside from that, there are no restrictions other than reasonable use.
Unless you are creating a whole new client for interacting with Gemini, you will likely be most interested in the public events endpoints, for integrating with your site in someway.