If your events are public, others can easily export them with JSON and iCal feeds. Totally open, no authentication needed.
For federation, follows and approvals are passed between servers and public events are federated between servers running our software. Over time, we hope to use #ActivityPub fully to trade data with other event software.
And some things we didn't mention! Many rough edges and a lot to do, but if you are interested or just want to let us know what you think of the idea get in touch. There is more on our website: https://www.theoccasionoctopus.net/
We can import iCal feeds online straight into events in your account. There is also a Read/Write API so you can program bots that add events; here's some Python code to scrape events from a website, for instance.