It is buried in the footnotes of the post, but the ultimate reason behind going closed source is that Google built their enterprise GDrive syncing client for mac off a fork of osxfuse. The original author of osxfuse feels entitled to some compensation for that and is doing his damnedest to make it happen.
It's also noteworthy isn't the "original author of osxfuse". In fact, Google is. So while I can empathise with the general complaint about commercial use, one doesn't get to make that complaint against the one company that originally started the project and released it under a permissive license.