This may be a silly question, but since the newer Mac systems are built on unix, is it possible to run a Mac app natively on Ubuntu? I'm specifically interested in the Coda development environment.
They're both POSIX systems but no. Most OSX applications rely on various libraries (eg: Cocoa -- like GTK but not GTK) that aren't open source and therefore can't be ported.
I think there has been some interest in writing a layer like Wine to replace things like Cocoa but as far as I know, nothing has ever come of it.