Benjamin Mayo, writing for 9to5Mac:
HBO Go is completely separate and will not migrate to Max. If you subscribe to HBO through Apple TV Channels, you can download the HBO Max app and log in with your Apple ID to access all content at no additional charge. If you get HBO through your cable provider, you may be able to use those credentials to access HBO Max.
Remember when this service was initially announce and there was no clarity about how it would work in correlation to HBO Now or the Apple TV Channels option? I’m glad we’re finally clear on all of this.
I’m gonna go watch some Fresh Prince now.
Update: It looks like HBO Max doesn’t want to play nice with Apple TV Channels, as it appears the service isn’t involved at all. Upon entering the HBO Channel in the TV App, you’ll see this HBO Max carousel which prompts you to download the HBO Max app.
Within this screen you’ll also be offered to connect to the service with your existing Channels subscription with HBO, and that process is painless. You’ll also be able to keep shows in your Apple TV Up Next queue. It’s just to watch the HBO Max content, you’ll be forced to use the HBO Max app, which is slightly inconvenient.