If you've used Editorially and enjoyed it, I'd like to recommend my own application that I am currently developing called Typewrite ( https://typewrite.io ). Though it's only been in development for about a month an a half, it is relatively inexpensive to run and I don't plan on shutting it down anytime soon.
It has live collaboration like Google Docs, and a simple interface like Byword, iA Writer, or Editorially. I'm working behind the scenes to add features and documentation and plan on releasing updates for it every so often.
That's a good start, but as you said is very basic. The JSON data would be useful for determining if a spot is taken but it doesn't have a nice way to view all the entries (without building that yourself).
Thanks for sharing. I've briefly examined the features of both services as well as other similar ones, but they all mostly focus on the front-end side and tightly integrate with the back end. I'm sure it's possible to hack together your own version of the font-end. However, that still wouldn't let me, for example, limit the number of sign ups for a certain event.
It has live collaboration like Google Docs, and a simple interface like Byword, iA Writer, or Editorially. I'm working behind the scenes to add features and documentation and plan on releasing updates for it every so often.
If you are interested in seeing why I created Typewrite, please read the first blog post at: http://blog.typewrite.io/2014/simplicity-in-real-time/