> there's nothing wrong with starting a business rebranding Nextcloud and keeping your development closed source, as long as you're honest about that, which this initiative is not.

I thought Nextcloud was released under the AGPL, making this very much not okay by default. So either I misunderstood something or Office.eu got a permission to make non-free modifications? (Going by what you said; I have not dived into this.)

If it just says that it is partly based on Nextcloud, that does not imply they modified Nextcloud code at all. Other parts of the platform could be based on some other code, even closed one.