Jonathan Corbett has a great update to his ongoing analysis of who writes the Linux kernel. By a wide margin, Red Hat remains at the top of the heap (12.7% as measured by lines changed). But perhaps most importantly, the group of developers "known to be working on their own time" takes the largest share (15%).
That's a lot of "free" labor....
Perhaps even more intriguing is Jonathan's reading between the lines in the data as to which companies contribute to certain parts of the kernel:
From these numbers, one might conclude that Red Hat developers are strong in the core kernel area, but they don't much like writing documentation. There is a lot of "hobbyist" participation in the driver subtree - not a particularly surprising result, since making a specific device work is a common itch for developers to scratch. Academics like to play with filesystems, as do, unsurprisingly, companies like Oracle and NetApp.
In other words, it's not surprising that just as individual developers scratch their own itches, it's also reasonable to expect corporations to scratch their particular itches. IBM and Red Hat care about different parts of the kernel, at least some of the time, and you can see this in the data.
I'm still waiting for Oracle to up its involvement in the Linux kernel, given that it's allegedly a big player in Linux now. But then again, where's Novell? At 2.7%, it can hardly claim to carry much clout in the Linux kernel community.
However, following the theme above, maybe Novell doesn't care as much about core kernel development, since it tends to focus as much (or more) on things like OpenOffice, Gnome, etc...?