Is somebody using the brand on something that isn't OBS?

https://bazaar.launchpad.net/~mozillateam/firefox/firefox.ja... is the config for what becomes Ubuntu's firefox package

https://gitlab.archlinux.org/archlinux/packaging/packages/fi... is the equivalent for Arch

Both apply different configurations, use different versions of dependencies, and in Arch's case applies a patch to the upstream code.

Which of them isn't Firefox?

I worked for a company that sold high-end imaging equipment.

They had distribution networks, authorized to carry their brand.

But there were also “gray market” distributors, that would do things like resell foreign market gear, or devices that were separated from sales promotion bundles.

These were our brand, but the company would not support them. No hardware fixes (unless paid), no firmware upgrades, and no marketing support.

Often, the savings were minimal. It was expensive gear; even at a discount.

whichever one(s) the owner of the name "firefox" allows to be called firefox. Open source code does not automatically mean you get to use the name of the project in your redistribution of it.