The fact that BeOS is single-user is news to me. I have to wonder what the security model looks like without a 'root' concept - this article's dismissal of the problem seems pretty shallow.
Obviously the "Change the World" title is just linkbait. Thanks for renaming.
Plan 9 has no super-user. Each server is responsible for maintaining its own security, usually permitting access only from the console, which is protected by a password. For example, file servers have a unique administrative user called adm, with special privileges that apply only to commands typed at the server’s physical console. These privileges concern the day-to-day maintenance of the server, such as adding new users and configuring disks and networks. The privileges do not include the ability to modify, examine, or change the permissions of any files. If a file is read-protected by a user, only that user may grant access to others.
IIRC BeOS had no security model; basically everything ran as root all the time. You might say that it had no concept of non-root. Remember that Be viewed Mac OS 8.0 and Windows 95 as their competition, not Unix.
Obviously the "Change the World" title is just linkbait. Thanks for renaming.