25 years ago, I configured GNOME to run a BeOS-like tabbed window manager. On a sun workstation.

But that's not what this is. Or not only:

Nexus Kernel Bridge

Nexus is Vitruvian's custom Linux kernel subsystem that brings BeOS-style node monitoring, device tracking, and messaging to Linux — making it possible to run Haiku applications on a standard Linux kernel.

It claims to run apps from Haiku, the current open-source implementation of a modern BeOS.