As pbnjay says, torrents alone can't be used because they target static content. I'm currently building an OSS alternative of btsync at https://github.com/rakoo/rakoshare.

Basically you can use a torrent to transfer content, but you need to transfer the new torrent itself some other way; I use bittorrent's extension capabilities to do that.

I also have very little low-level bittorrent experience, but the static nature of .torrent files would be tricky. You'd need some sort of snapshotting diffs to convert to .torrent equivalents at regular intervals, right?

Isn't syncthing https://github.com/syncthing/syncthing, supposed to be an open source alternative to btsync ?

I wonder if it would be easier building an open source version of btsync 1.4 as 2.0 seems to be a lot more complicated?