That is really underselling what is happening here. This is fundamentally a complete success of the open source collaborative model. Ie why did Sun choose Linux for Ranger? Simply because of the incredible work and effort that other companies, the Labs and so on have put into making Linux actually work at this scale. The pace of technology change in the HPC world is very fast, and quite simply no single vendor can supply a complete software stack and continually rev it every 2 years to keep up.
At the HPC level, you take the latest and greatest hardware platform and Linux is the first (sometimes even ONLY) OS to fully support all the hardware in the box. Many companies are involved in making this happen and it is driven to a large degree by demand for Linux based compute resources from the customers.
One unique thing about the HPC space is the major customer demand is very strongly aligned with open source principles. The major US Labs that run the biggest machines *demand* from their vendors open source solutions, period full stop. They do this entirely out of their own self interest, after decades of vendor abuse and neglect.
If this model can work in the HPC space, it can work in other spaces too. We see strong similarities in the embedded space as well.