There are many P2P file sync systems like AeroFS and Tonido. One thing that BitTorrent Sync stands out is that it doesn’t require account registrations. Other services require creating an account prior to use. It almost makes me “why do I need to register to use a P2P system?” With BitTorrent Sync, it is as easy as exchanging a key.
You can try read only key of RBU7XLPET43IWGFSLNJEGREIOZI6V4YE2. It’s a repository of Emacs build for Windows and Mac.