It is possible, but I’m not sure if you are describing the possible way or the not possible way. It depends who owns
If the app owner owns that, they own the subNames too. But
JamsUsersPublicName public name reads to me like the user owns it, in which case they own the subNames too.
The latter means that there is a copy of JAMS app at the user owned
I’m not sure if that’s what you have in mind, but it is possible, easy to do, and won’t use many PUTs because they won’t need to pay to upload the JAMS source files, they will just reuse the XOR addresses of the source files.
This is how I envisaged users can own their own SAFE Plume blog, I just didn’t get around to implementing if fully yet. One day!
So to summarise, a user can effectively run a copy of JAMS on their own publicName, and would then own the
demo subNames on that publicName, and your app could set this up for them with a ‘create my JAMS’ command which registers their chosen publicName, and makes an instance of JAMS there.
That may not be what you have in mind. An alternative is for the app to be at one location owned by you as developer, but the user’s music stored and shared by the user at a location which they own. I’m not sure if this is what you have in mind, but it might be sensible, I’m not sure. I’d have to think more about that.