The fork is called EuroOffice and will be released next month. Onlyoffice is from Russian developers and includes binary blobs, it's not fully open source.

I tried it just a few days ago, and I can't recommend OnlyOffice. Well, I am not an MS Word user, but I think even MS Word, at least the desktop apps, used to support styles better. What I mean is naming and defining various types of styles, paragraph styles, character styles, table styles, etc. OnlyOffice basically has no character styles that work properly. What you can find online about how to do character styles are hacks for using paragraph styles in such a way that they become character styles. But they are still mixed up with paragraph styles at the top style selection bar thingy. Of course this is an area where LO excels, above and beyond MS products. But I have come to expect what LO can do in terms of styles as the baseline. If a word processor can't even give me those style type choices, it is a child's toy, for writing actually well made documents.