Hmmm...I'll check. I know I have a license key, but I can't recall if I bought it or if it was a free-for-personal-use license. I'll test it.
Ok, when I got RealVNC v4 and upgraded to v5, I got the free-for-personal-use license from their site, as you had to have some kind of license key from them in order to use RealVNC. I haven't tried v 6 aka VNC Connect, but they have a free-for-5-PC connections home license. It seems to be cloud-based, though, and I don't see any reason to have my PC's access the internet for this.
So, I'm using my RealVNC 5 installation. If you have that...
1) install and fire up VNC Server (I tend to use user mode, because I don't want it running all of the time).
2) I'm not changing anything in the normal options.
3) Go into the Expert Options, and update QueryConnect to "True", and set the QueryTimeout to a value (I use 20 seconds).
If you set the QueryTimeoutRights to "sv", then the default option used if you do nothing in response to the connection query pop-up on the server will be view-only. This is important!
While you are in there, look for TimeOut, and set the ConnTimeout and IdleTimeouts to 0 to disable them.
4) Connect from the remote machines. When you do, a pop-up will appear on the server for 20 seconds.
If you click on "Accept", that remote viewer has full control. If you select "view-only" or do nothing, then the connection will get view-only access.
5) I generally only have a few machines running in the room.
6) You can check the usage of any connection by right-clicking on the VNC icon in the notification area (should be black with VNC in it if there are connections) and clicking on Connections...
And that's it! I haven't tried VNC Connect yet. I'll give it a whirl on one of my PC's to see if I can set it up to use a LAN connection with the "free" Home licensing, or if I have to use their cloud services.