

Technically, according to the GPLv3 you don’t need to make the source code publically available. If you sell software with binaries then their source code must be included with it. If you’re Red Hat you can also add an additional ToS to the website that states if you buy the software you can’t freely distribute the source code you download from the website or you will be sued to oblivion.
Iirc the openXML standard was open sourced due to some anti trust stuff brewing. They then expanded on the standard with proprietary addons that give LibreOffice/Google Docs trouble.