FSS are the creators or AGPL3, aka. The liscence OnlyOffice is released under.

FSS made a statement/blog-post to come out and say the restrictions OnlyOffice added is illegitimate and not in accordance with AGPL3.

OO isn’t just asking for attribution they are asking two things.

1. You must keep out logo
2. Nobody is allowed to use our logo

Do you see the problem, it’s not just attribution