Only the foreground app gets to put things in the touch bar. Excellent - I don't want some background process putting animated ads there.
Beyond that, Apple can't possibly limit what the foreground app does. Distribute your tasteless animating app with a Developer ID cert, and annoy people to your heart's content.
I do want a screensaver that also uses the touch bar. Nyan Cat is acceptable in this context.
If I had an application that advertised to me like that I'd just uninstall it immediately, like I do on my phone.
I think a lot of people in this thread are getting so riled up about bad design the only alternative they see is totalitarianism.
In this case I think if you're giving an application your focus it should be able to use a secondary screen however the user wants it to. If the experience is bad people won't use your app.
Apple is instead saying "we know what all the good experiences are, so don't go having any bright ideas" — hopefully they won't strongly enforce any of their "guidelines"
Beyond that, Apple can't possibly limit what the foreground app does. Distribute your tasteless animating app with a Developer ID cert, and annoy people to your heart's content.
I do want a screensaver that also uses the touch bar. Nyan Cat is acceptable in this context.