The Document Foundation has launched a scathing attack on OnlyOffice, accusing the productivity suite of being "fake open-source" for partnering with Microsoft to enforce vendor lock-in. TDF claims OnlyOffice promotes Microsoft file formats instead of championing open standards, echoing Microsoft's past tactics that trapped users in proprietary ecosystems.

This battle mirrors the browser wars of the early 2000s, according to TDF, when Microsoft attempted to control web standards through Internet Explorer. Unlike the W3C's successful resistance then, the organization argues ISO failed when it recognized Microsoft Office Open XML (OOXML) as a standard despite its proprietary nature and ongoing compatibility issues across different platforms.

Users face constant formatting errors when reading Microsoft documents outside Microsoft software, TDF contends. The foundation warns proprietary formats act like "digital handcuffs" protecting Microsoft's $30 billion business, forcing users to entrust their content to a company whose interests may not align with their own. OnlyOffice defends its hybrid open-source/proprietary model as meeting market demands while maintaining compatibility with the dominant office suite.