Thanks for your prompt reply!
The latest version of the installer threw an error as it wasn't able to download NDP46-KB3045560-Web.exe but I simply downloaded and installed it manually, then ran the installer again -- thanks to the very helpful information provided with the error message. On the second pass, the installer recognized the presence of .NET 4.6 and bypassed the download/installation, and completed its work successfully.
Upon running TuneBlade, the error pop-up window didn't immediately appear this time around, so I was able to use TuneBlade setup, enter the license, and then use it to stream to several AirPlay speakers from my J.River Media Center source -- perfectly synchronized.
In summary, your latest release works beautifully! Hope an Android version of your remote control is in the works (or even better, J.River integrates the functionality in their remote :-) ).