Good news, I have implemented the most basic stuff for the new backend of the download client. Most likely, it's still a little rough around the edges, however, since I'll be on holiday in a week, I do want to release a new version in a couple of days to minimize delay.
I think I'll be able to release Wednesday a new version.
I had some trouble getting the uploading of torrents working. It seemed that they had switched to a non-standard implementation of uploading files not conforming to the HTTP/MIME standard. However, I misinterpreted the output of the packet analyser and uploading is working now.