Software Freedom Conservancy

Microsoft & exFAT: One Step on a Long Journey

by Karen Sandler on August 30, 2019

In 2013, Conservancy helped resolve a GPL violation by Samsung which arose primarily due to complications around Microsoft's patent holdings related to the exFAT filesystem. At the time, Microsoft was known for demanding patent fees from Linux users and redistributors.

Late last year, Microsoft joined Open Invention Network. As we wrote at the time, this action had limited impact, as key patents like exFAT were not implemented in any packages that were part of OIN's “Linux System Definition”. We asked Microsoft at the time to upstream the exFAT code under GPLv2-or-later to confirm its intention to end patent aggression.

This week, in response to recent follow-up requests from upstream Linux developers, Microsoft announced that they would sign off on inclusion of exFAT in upstream Linux. This is the first step toward real patent peace related to exFAT.

This process for exFAT will only complete once all of the following happen: the exFAT patch appears in an official Linux release, that official Linux release becomes part of OIN's Linux System Definition (this generally happens automatically, as future versions of Linux are included by default), and Microsoft distributes a copy of Linux themselves that contains this technology. This last step is critical, as the OIN patent license is not as comprehensive as a full patent license from Microsoft. Any participating company can withdraw at any time from OIN1 (and there have been several withdrawals in the past, including Oracle, Facebook, HP and Symantec). After a transition period, the safety of OIN's non-aggression pact weakens. In contrast, when a company distributes software under the GPL, there is an irrevocable implicit patent license with the distribution, and GPLv2§7 further assures patent licensing safety.

Eventually, Microsoft will likely distribute a version of Linux containing exFAT to its Azure users and in its Windows Subsystem for Linux. However, until that occurs, the issue is not really resolved. An expedient solution is as we previously requested: that Microsoft bring definitive patent safety to free and open source software by publicly granting a permanent patent license for all patents Microsoft holds that read on Linux. Additionally, we invite Microsoft to keep pace with its peers such as Google and Red Hat, who years ago made very public patent promises to FOSS users. While the actions taken thus far are intermediary steps, I applaud Microsoft's journey from being a company that long attacked FOSS to becoming a contributor.


1 The legal mechanism for withdrawal is exercise of a “Limitation Election” in the OIN patent license agreement.

Tags: conservancy, patent, law

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