Does Renoise work with Core Audio drivers?
Or does software have to support for it at all in order it to work?
renoise uses the core-audio-driver, yep. all good.
if you were to install a different window manager onto OSX (ie: KDE, GNOME) would you still be able to run Renoise?
Well…
Personally I’d Stay away from X11 based apps on the Mac.
The trend is going towards native Mac OS X apps without the need of a X11 based windowmanager.
Before renoise i used two apps on the mac for tracking, PlayerPro and Soundtracker(wich was pretty easy to get running thanks to the Fink project), CheeseTracker is just plain nasty.
So unless Backis decides to go X11 with Mac version of Renoise i doubt you’ll be able to run Renoise with a different windowmanager.
i’m just asking cu zi like the KDE gui better. (gadz! a mouse with more than one button?)
It sounds like you never used a Mac.
You can’t just install another window manager in OSX. You can only run X11 and assorted software on top of Aqua. You can’t disable Aqua and fully run X11. You might as well install Linux and dual boot for your audio needs (but why buy a Mac for that?). 
But… you don’t need KDE (or something else) to use a multi mouse button. MacOS X fully supports multi button mouse (and scrollwheel) out of the box. Still, the lack of snappiness in Aqua (on a G4-800) was enough reason for me to prefer Gnome.
Mac renoisers have all the luck though! They get CoreAudio in the non-registered version and we only get ASIO with the registered one? 
Hehe…
In case you’ve missed it you can use just about any USB mouse with the Mac.
The the OS X GUI is ‘right click’ aware, scrollwheel aware etc, no need to install drivers.
Then again, to get Renoise running under X11 the Renoise team would have to consider Linux port, untill that happens i see no reason to implement X11 support in the Mac version of Renoise.
My best guess is that Blackis feels this way about this too.
Just to clarify the situation a little:
As has already been mentioned, you can’t just replace Aqua/Cocoa with “another windowmanager”, Aqua/Cocoa is so much more than a window manager.
You can run X11 without Aqua on MacOS X (in the login window, login with username “>console” and MacOS X will turn off Aqua and look pretty much like any unix out there). But this will not let you run Renoise as it requires the functionality that Aqua/Cocoa provides.
In the future there might be a port for linux/other unixes, and this hypothetical port would be pretty easy to compile also for MacOS X with X11 but honestly I don’t really see any point in doing this, it would just be another version to support which wouldn’t fill any need.
If you want X11 applications instead of native MacOS X applications, I don’t understand why you would be using OS X in the first place 
- Simon