I'm confused and couldn't find an answer searching for "xdg-app" in AppImage's website/github. Is this a whole alternative to xdg-app, or a layer on top of it?

I'm confused and couldn't find an answer searching for "xdg-app" in AppImage's website/github. Is this a whole alternative to xdg-app, or a layer on top of it? If it's indeed an alternative, why would anyone choose this rather than xdg-app? xdg-app being backed by fedora/freedesktop/gnome folks might mean more traction and maintenance, doesn't it? EDIT: okay, saw https://github.com/probonopd/AppImageKit/wiki/Similar-projects https://github.com/probonopd/AppImageKit/wiki/Similar-projec... mentioned below by the author, sorry for the noise.