In the class, we'll learn programming in linux environment accessed through Cygwin/X. You should install X-window system to your desktop computers to do assignments etc.
The programming skill you learn in the class should be applicable to any platform. If you want to develop programs directly on your desktop computer (without connecting to linux server), you can install the developper tools. But they are not required for this class.
If you encounter problems with X11 included in OS-X 10.5.1, you can update with the latest release.
Double Click "Optional Installs" after inserting the Install DVD.
Under "Applications", you can find "X11".
This blog has lots of great tips about Fink.