No more need to manually download tracks you previously uploaded to openstreetmap.org first, then opening the downloaded file with JOSMs "Open file ..." dialog. You can now pick an uploaded track and have it loaded into a new GPX layer directly with the help of the DirectDownloadplugin.
You can download the compiled plugin .jar or the source code, but be warned: current status is "works for me" aka. "proof of concept".
The desired functionality is there, but it still is a bit rough around the edges.