I would think that any module added to a portal, regardless of which alias was used to add it, should be accessible to all aliases for that portal.  If you want to limit access, do it by user roles, not aliases.  To me, it defeats the purpose of multiple aliases if you can only view a module added by an alias when accessing it from that alias.  And if that's the case, then why even be able to view the module at all from another alias?  I think this is just a bug in a Beta module.

If a host wants to have multiple galleries, they can across multiple portals.  But not in the same, at least not with this particular gallery module.