A private household assistant. Not a public service.
Noura is software Drake built for his own household. She runs on a single Mac in his home office and helps one family keep track of its calendar: reading what's coming up, and adding or moving appointments when the family asks her to.
She isn't offered to anyone else, and there's nothing to sign up for. The only Google account she signs in to is her own.
How she handles Google data is set out in the privacy policy.