In terms of privacy, nothing would change, it’s still the same as ever so I think the recommendation can absolutely stay up, even proprietary apps are suggested on Privacy Guides.
In terms of software freedom, this is a terrible change and I really dislike projects moving to source-available models, in this case, as the other commenters said there, I don’t even think it’s legal, unless every contributor has signed a CLA in the past.
I feel for not wanting to be explioted by corporate, but they could have gone the dual licensing path and instead chose to restrict everyone’s freedom, even us users. Now that doesn’t mean forks can’t be made I believe, it’s just that anyone who does that, won’t ever be able to sell the service which could be unsustainable since they made the server CC-BY-NC-SA, that’s a big turn off for those who want to host that