How does junk like this get posted on a tech web site. This is the built in VNC client and is very publicly shipped with OS X, and it has nothing to do with Apple's remote desktop.
You could always do CMD+k to bring up the "Connect to server dialog" and type
vnc://ComputerName.local
to VNC into it (if screen sharing is configured in the system prefs on the target machine).
Ironically, I wrote this back in 2011 and someone else submitted it earlier today. :D
The thing is... Apple doesn't make this feature prominent. The only real consumer-friendly way to access Screen Sharing was through iChat back in the day. The Application is buried within the System folder and most people think you have to pay $50 USD for Apple's commercial Remote Desktop solution.
Most people don't need all of the features of the full client, such as remotely installing packages or managing machines. They just want to access their machines through the LAN or through Back to My Mac. https://www.apple.com/support/icloud/back-to-my-mac/
It's not the same software, but it's basically a scaled down version to get the job done.
You could always do CMD+k to bring up the "Connect to server dialog" and type
to VNC into it (if screen sharing is configured in the system prefs on the target machine).