As I mentioned, I was able to run 2 downloads if I started one from JD, then 3 hours later when the 1st was still running, via the browser. No login on either. I was testing something that someone told me was possible via another forum. So I was just trying to see if I could do it via JD. Apparently not, as the plugin is hard-coded to allow one and only one download if in no-account mode.
It used to be fairly common that even though a site claimed free/no account users could only download one file at a time, you could usually start a second download if the nominal "wait time" had elapsed. It's pretty uncommon now, but uploaded is one of the few it still works with. That's because they base it off when a file download STARTS, not when it ends. So, 3 hours after you start one download, you can start another, regardless of if one is still running or not. Of course they don't advertise it- it's probably exploiting a bug in their system.
It's only useful to me on those "highly restrictive sites" since they have such long wait times and slow speeds. I don't use those sites much anyway, especially on large files- just whatever I can get out of them to reduce the queue of files on better sites, or when every other mirror I've found is dead.