BlockNote XL packages are features provided by code available either under the Affero GPL license or if the user is a sponsor. See the note in BlockNote release v0.19.0, where @YousefED wrote:

To ensure we run a sustainable project, we are experimenting with XL packages. These are dual-licensed packages that are released under AGPL-3.0 licenses. You're free to use these in open source projects, but for usage in proprietary / commercial projects, a sponsorship is required.

DINUM uses two XL packages for docs.numerique.gouv.fr, its own instance of Docs: this is made possible without forcing DINUM to publish its source code as AGPL because DINUM is a sponsor of BlockNote.

But DINUM is also including XL packages directly in Docs as an open source product shipped for others: see these lines.

This should be fixed by not including XL packages in Docs by default: it is the responsibility of the Docs reuser to include these packages and either become a BlockNote sponsor or adhere to the AGPL licence.