Ross Ramsay, one of my Patreon supporters, asked:
I was just curious if you had any plans to incorporate Dropbox or some way to synchronize and collaborate with the program? If you eventually add some kind of mobile system for this, it would be almost needed to sync between devices. As is, I'd use it to work with others, and sync between my work and home computer. With the ability to sync in some way, you might be able to use the mobile platform instead of having a dedicated mobile version for iOS and Android.
One great weakness of Twine is that it has no real way to collaborate with other authors. When I originally created Twine as a desktop app, sharing a Twine story meant sharing the file through whatever means at hand-- email, a network share, Dropbox, what have-you.
Technically speaking, this option remains in the Twine 2 era. But in the era of Google Docs and Office 365, expectations have changed. Not only do people not want to mess around with file sharing -- the expectation is that data lives in the cloud, which is to say "someone else's server" -- but there's also an expectation that multiple people should be able to edit simultaneously. These are not unfair expectations to have! In particular, the idea of simultaneous editing just makes sense. But they impose additional levels of complexity on an application.
(It reminds me of the shift from modal, text-based applications to event-driven GUI apps. I am not old enough to have actually worked on an app back then, but I remember reading about this in programming books I devoured as a kid. In both cases, a fundamental change in perspective was required.)
I decided very early on in the Twine 2 design process that I did not want to be responsible for storing stories on a server I controlled. I've seen other systems -- and continue to see new ones crop up -- that do this, and when this happens, authors become captive audiences of those who run the servers. Without some kind of financial means to keep the lights on, these services only exist so long as their maintainers have interest -- and in most cases, that can be measured in years, sometimes months. Imagine writing a story that just disappeared five years later! It would be a strange, even outrageous idea in the physical world. And yet we accept such ideas without much more than a sigh when they occur online.
There were other concerns to running a centralized Twine server, too. I believe that as long as you house content, you share responsibility for it -- though this does not seem to be an attitude that everyone shares these days. I'm speaking here in moral terms, not really legal ones. I understand what safe harbor provisions are. Policing content for odious stuff like racism, pedophilia, and so on is not something I want to do. It's a thankless but necessary job.
I also looked into integrating with services like Dropbox, but in my limited exploration, I found that they expected you to have your own server backend that will talk to their services, not have clients speak directly to them. Twine 2 doesn't have a backend. In this respect, it still resembles its TiddlyWiki parentage. An important cavest -- my understanding of this might be outdated. It's been some time since I did that exploration.
In short, I would very much like to work on a collaborative Twine server but I don't have the time or resources to do so right now. And before I started working on it, I'd need a real plan for sustainability that I was confident in. It would only be fair to people using it.
That said, I consider this subject an open question, not a sad conclusion.