Yeah the lack of open source prevented me from committing to observable, too, so I look forward to trying dataflow out.

Just in case this is of interest to others, some other open source browser-based computational notebook tools include:

* Starboard https://starboard.gg/ * And of course there's always Jupyter, but it requires a server component

And this isn't the same thing, more of a javascript playground (open source alternative to codepen and the like), but see also Slingcode: https://slingcode.net/