I loaded 57 and get the same thing. I purchased the software and really like it. Just need to tidy up the installation.
I guess I just don't under stand the issue. Download. Then click on the download. Install it then drag the "JRiver" icon to the desktop and open it. That's it! You can move the JRiver Icon to the dock if you choose but I just leave it on my desktop.
When an upgrade comes out, it take me 20 seconds to install it and run it.
I also delete the icon from my desktop before I drag the new one to the desktop.