Someone could write a viewer, or converter for this format? Should be simpler than writing a new creation app.

You could, but why? I wrote a small package to automate my backups, and transform the content into something readable for myself. It's far from feature complete, even for my simple personal use.

But if you're doing a complete read-only copy of roam, why not go all the way and make it editable, and compete with them instead?

If, like OP, you are concerned about the closed nature of Roam, you could make that converter instead of a replacement for Roam.

You could say openness is “a feature, not a product”, and it’s a feature that could be retrofitted.

You could, yeah.

You could put in a lot of work, just for read-only feature parity.

Or you could work some more, and have a competing product.

You seem adamant, that the former is a better path, but I don't quite see why would you do all that work for naught.

(Roam already broke my backup script 2 times, and there are better uses of my time than interfacing with a proprietary product, if there are better alternatives.)

I'd say a parser is an order of magnitude less work, but if someone wants to make a full product I'm not going to try to stop them.

That's fine. I'm quite happy with roam, I have the exports if I ever need them.

> I have the exports if I ever need them.

Do yourself a favor and check if the exports actually have what you need, before blindly trusting it.