They're... not? "Backstage" is a noun. It's a place. It so happens some entertainment industry publication uses it as a name, and a piece of software that is totally unrelated also use it as a name.
It's capitalized in the title, so it's a PROPER noun. And I've worked in software development for a long time, and have read HN regularly for a long time, and I've never heard of "Backstage" as software.
There's a wide world out there, which some HN posters "forget."