I tried out the unbranded builds linked from here . I noticed that they were branded "Nightly". I think this is very confusing. The name "Nightly" already has a meaning in the Firefox community - a less-stable-than-release build reflecting the latest development work which is updated every day. The unbranded build is something very different. Moreover, the audience of the unbranded builds (add-on developers and power users who wish to run unsigned addons) is relatively likely to have heard of the actual Nightly channel and perhaps even have it installed concurrently, making the confusion even more unfortunate. Please consider naming the unbranded build something else, such as "Unbranded" or "Add-on Developer".  https://wiki.mozilla.org/Add-ons/Extension_Signing#Latest_Builds
All unbranded builds on our ci farm are called nightly. I just downloaded a ci build from mozilla-inbound and it was called branded nightly. This is the default branding for non release/beta etc builds. The intent was to have the builds that allow the installation of unbranded addons look just like ci builds.