Here maybe a solution to speech in X Windows:

[Saqib Shaikh]

But by default OS x doesn't have X on it.  Sure you can run X on it, but the
screen reader will only work with the native GUI - that is, with Carbon or
Cocoa based apps.  I love the Mac and have been working on it for a while
now, but *not* because it is like Linux, but precisely because it is
different, with its own advantages/disadvantages.

Just as a total aside, you could run Gnome/Gnopernicus on OS x, but then you
would only be able to use Gnome apps and not OS X apps, which IMHO defeats
the objective.

Saqib Shaikh