In a blog post, OnlyOffice publicly expresses its anger. Euro-Office is using technology derived from OnlyOffice in violation of license terms and international intellectual property law. OnlyOffice is subject to the AGPL-v3 license and imposes further conditions to ensure transparency and appropriate source attribution. According to OnlyOffice, these include retaining the OnlyOffice trademarks in derivative works, providing appropriate source attribution to the original technology, and fully complying with open-source requirements for distributing the software.
This is the nightmare scenario for companies doing open source software. Regardless of how OnlyOffice behaves and their russian ties - other companies forking the whole codebase, removing the name and selling it is something that will prevent others from going the FOSS route