Taskserver and Taskwarrior
Taskserver allows users to synchronise their Taskwarrior instances across multiple locations.
I had also thought perhaps to add a WebUI as well, but it looks like the two I know of are now un-maintained which might be an issue:
Inthe.am kind of provides the idea. I don't know if this is too much work, because it looks like more than just packaging Taskserver and Taskwarrior:
Actually just noticedInthe.am is open source anyway. Perhaps it's possible just to package that.