I wrote to MyMuse and got an instant answer. The guy helped me to install it, set it up and even modified it to suit some of the things I wanted to do.
The product does everything it says it can do and more. It's easy to install, offers all the security to stop the thieves and the idiots who download everything in sight "because they can".
There are an awful lot of options to configure, so you can sell just about anything and the support is absolutely outstanding.
I have already set up 2 Joomla sites using MyMuse and I'm busy on the third.
It's a brilliant product! 100% recommendation.