HackMD is a nice open source software for editing documents with Markdown markup collaboratively.
We have used the hosted instance for taking notes of IRC meetings.
It was offline once for half an hour during one meeting because of a bug.
To be more independent we can setup our own instance.
- Node.JS 4.x .. 6.7.0
Postgres seams to be the preferred database (used in docker image).
The Instance would be public unless we configure BASIC AUTH but i think that's ok. It's only text, no BIGDATA.