I had a go at porting this over. I never used the original so I don't know what most of the other functions do, but I wanted to be able to read calendar events in Hubitat 
It works for showing the next event (with optional filter) using the Contact/Event sensor type.
I didn't test any of the notification stuff (would prefer to do this via Rule Machine myself, unless there is some reason it's built into the app itself?), and didn't test the Presence sensor type either.
But it's a start - feel free to modify as necessary!
Note: The connecting to Google part is a little clunky, as you'll have to go out to a separate tab and enter a code, but you'll only have to do the linking once.
(Couldn't get the original web flow to work with Hubitat because both Google and Hubitat wanted to use the access_token parameter when returning the callback to the app).
