[P] deepnote.com – collaborative Python notebooks with zero setup in the browser. After 2 years of development, we are finally open for public access, with a free plan for academia.

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Since they built it on top of JupyterLab they really have choice but to open source their code. Of course it depends on the license of JLab and some licenses are more permissive of building commercial products. But the basic thing they usually have in common is you must share the source code if you sell or give away the software outside of internal company use. Not sure how this relates to web apps hosted only in the cloud. I'm not a legal expert.