AMD bought out ATI several years ago. So they make both now.
I've never seen an AMD graphics card, or an ATI processor. That's akin to saying that Pepsi makes Dr. Pepper, when they're two separate brands. One may own the other, but there's certainly the distinction in the product.
Edit:
Uhm, I'm pretty sure Rage does require OpenGL and not DirectX... otherwise I'd be playing it right now.
How would a game using OpenGL not be playable?