ATI Catalyst is closed source, echoblack. "Catalyst" may broadly refer to both video management software as well as device drivers.
The OpenBSD Project,
by policy, does not accept any closed source code or any closed documentation in the OS. For any purpose. Ever. And as for binary objects, or "blobs", please see the
commentary and lyrics to the song for OpenBSD 3.9
Closed source or binary objects are possible only in two places, because these are not part of the OS: peripheral device firmware, and the ports/packages system.
It is possible to have 3rd party ports/packages which are kernel modules -- emulators/kqemu is one example. So it may be possible to have a closed-source driver for OpenBSD. Possible. I can't see ATI bothering for so small a market.
But ... no bugs are ever accepted by the Project when the kernel contains a 3rd party module. You'll be told that you are running a "Frankensystem," and when it breaks, you get to keep the pieces.