https://www.reddit.com/r/etymologymaps/comments/g4bmh3/chai_...
A board is just one implementation of this signalling process, but by no way implied by it.
Any open source equivalents?
But from the home page I don't directly get whether this is backed by markdown flat files or some other system, do you know?
Obsidian may not be open source, but it reflects a sane approach to product: small, focused team, profitable company, delivering useful stuff. Clean and tight. It's got a different set of abstractions at its core (document model vs block model) but if you're indifferent to that, Obsidian is where I'd start.
0. https://github.com/benchristel/benchristel.github.io/wiki/
https://docs.github.com/en/communities/documenting-your-proj...
Otherwise it's a lightweight alternative to Obsidian Publish. The disadvantage, that it's limited to a common subset of GFM, Gollum, and Obsidian Markdown.
That predates plugins being native on mobile apps however, so the built in Obsidian Git plugin might be better now.
However, you can choose to backup and sync your workspace across multiple devices using a cloud service. The most pain-free way to do this is by buying a subscription to Obsidian Vault. This is also a good way to support the development team, since the main product is free. When you store your workspace on Obsidian Vault, you can choose to specify an encryption key, so that theoretically nobody at Obsidian should be able to read your data.
But there's nothing stopping you from using other cloud storage services. There's even a community plugin you can find to use a Git repo for storage.