Hello. I've planned to share photos with my friends from NAS via WebUI, but WebUI doesn't accept Russian UTF-8 folders on my NAS (there is bug in webui.js). Unfortunately, btsync doesn't have any public API, but it has WebUI in Linux version ! I've created simple console tool btsync-cli that communicates via WebUI. It can add shared folder or remove it from sync index. Another useful tool is php bittorent-sync-client for btsync WebUI. You can build your own server-side WebUI Now I'm working on standalone (you'll can install it on your hosting) photo sharing site via btsync. I hope this will be useful to someone. PS: btw, btsync process will crash in some cases if you call invalid urls with parameters..
