From what I understood: ONLYOFFICE is a fork of Libre Office by a russian company. NextCloud was using ONLYOFFICE for its built-in cloud office suite replacement. Then they forked it with others to have greater control on the software with no communication whatsever to the company developing ONLYOFFICE without respecting their questionnable trademark restriction within ONLYOFFICE licence which I am still unsure if it was compatible with GPL licence Libre Office is using.