On Mac, we can have a free version of RealVNC Viewer installed by using MacPorts.
Just install MacPorts base program and then from terminal, run the following command...
sudo port install vncviewer
After finish installing the port, launch Vnc Viewer by type...
vncviewer
...in the terminal and press enter, or you can create a shortcut in X11 for faster launch later.
http://www.macports.org/