Okay, quick silly question - the earlier 2.x versions of the Linux kernel are still being developed for what reason? Maybe to continue supporting older hardware or "just because?"

In commercial and scientific circles, once you get something working the way you want it, it's usually a good idea not to mess with it too much, and many organizations don't upgrade things unless absolutely necessary. So there are a good number of legacy systems out there that still require support and security patches.

Older kernels are also often a good choice for embedded systems that don't need a lot of the heavier, more advanced stuff that's been developed since.

2.4 is still in extensive use in some limited application areas (embedded as has been mentioned) and compact distros.

Really, its not so much 'in development' as having fixes and backports. The fixes are for things like security flaws, which have later turned up, and the backports are, generically, to make it work, at a system level, more like a 2.6 kernel, so that higher level apps see the same interface and don't have to maintain two codebases and to allow it to work with newer interfaces and devices.

So, the way I see it anyway, its more like 'maintenance' than 'new development'.

Okay - that makes sense. I didn't think about embedded systems and things like that.

All together now . . . "duh!"