"Unix-based NonStop fault tolerant clusters"
Tandem systems (mostly) run an OS called Guardian, quite distinct from Unix (though there are some similarities).
As is usually the case at IBM, the official convergence is often announced long after various product lines were already well on their way toward a confluence behind the scenes. And so it is with a new unit of Big Blue's Systems and Technology Group, which put all of its operating systems and hypervisor virtualization software …
"Now it is time for IBM to get serious and buy Red Hat before Oracle does. In a pinch, snapping up Citrix Systems and Novell would also do."
I'd agree that one of the major Linux players makes sense from IBM's perspective, but I'm not sure that gaining control of both Red Hat and SUSE, through Novell, would be a great idea, and it certainly wouldn't for the wider Linux community.