Not officially but people have managed to reverse engineer it before in order to host their own - forum.snapcraft.io/t/…/27109
Whilst I do get the sentiment (and in no way do I support Canonical in keeping it proprietary), how likely is it that alternative Snap repos are going to show up if they did make it possible? Even with Flatpak where it is encouraged and documented I don’t think I’ve heard of anyone setting up a Flathub alternative of any significance.