UltraVNC is Windows-only software. It interoperates with any VNC platform that keeps to the standard, though.
Google, Bing, and Yahoo (to name a few) have search engines that comb most of the digital information available on the network of computer systems collectively known as the internet. I would suggest going to one of those sites and see what they can offer in terms of Mac supported software.
www.google.comwww.bing.comwww.yahoo.com