Linux is not an OS – Linux is a kernel.
Where as many others in our industry start with a Linux distribution and pare it down, we started from scratch and it has only exactly what is needed to run RoonServer. Your assessment of their OS would be true, but ROCK is much trimmer thing.
ROCK runs almost nothing other than RoonServer, it boots in under 2 seconds, even things like the SMB server has been trimmed to only need the basics for exactly what you need to run RoonServer and work with ROCK.
I just explained this over here: