Just me on both accounts. The site is open source so occasionally we get volunteers that work on a project or two, but currently it's just me sailing this big ship of worldbuilders.
I do use some external libraries though; for example, the forums are another piece of open source software made by others (that I've made modifications to in order to integrate it into the site), so any time they update them we also get updates… which is almost like having more devs. :)
Hopefully! :)
You can share timelines with others to view right now, but there's no way to collaborate/edit them with others yet. That's on the wishlist of things to add, though! To share them, just click the share icon at the top-right when editing one and toggle it over to "Public", then share the URL it displays.
It looks like this:
