Apple definitely does provide a VNC service for OS-X Tiger. Not for previous ones, but yes, for Tiger. The problem is that they have mucked with the VNC protocol enough to make it incompatible with vnc4, which is "the" standard vnc (from realvnc.com ), in order to tie it to their expensive commercial "remote control" software solution. The result is that "normal" vnc clients tend to crash and die with messages like "unknown message type 242".

Solution: Go with "Vine Server" (OSXvnc) from Redstone Software, which is free and interacts fine with vnc4.