I appreciate the effort to imporve security awareness, but is such a website legal?
Then using a VNC client in the same way would fall under the same legal purview. I think as long as there is no interaction to carry out functions, attempt password/username combos, then it's fairgame.
Browsing to an address with your browser is like checking to see whether a shop on main street is open right now. Attempting to connect to a an address with VNC is more akin to walking around the back of a house and checking if the rear door is locked or not.