I don't know much about this, but I understand Project Jupyter is Nonprofit. If I go to "jupyter.org" I see a tab "Community" and another "Governance". If I go to "deepnote.com" I see "Customers" and "Pricing".
Why would people want a standard to be controlled by a private company? I don't think the "Open-Sourcing" of it says enough. How does licensing work with formats or standards?
All standards are ultimately controlled by private companies. Even non-profits require funding.
Open source always depended on a viable business model (of one or many companies) that can sustain not just the release, but also an ongoing maintenance of the standard.
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People don't want that. This article is largely empty marketing. Claiming they have "the successor" is all you need to read before you can infer it's hot air.