Since always. For clarity, they are using the commercial offering from backblaze, not backblaze's personal/home use product.

B2 is similar to s3, and B2 charges for api calls + egress. Ingress is free, and they have a generous free daily api calling limit that covers some of the core api

It looks like downloading is free with their personal backup service, but is $0.01/GB with their B2 cloud storage service.

Backblaze B2 is different than Backblaze Backup.