Linux kernel swear counts per version
vidarholen.net
vidarholen.net
EDIT: my advisor likes it better, and it actually makes really pretty graphs.
But upon further reflection, I think that's probably the first occurrence of 2.5.x. That was an experimental version, and probably had lots of old subsystems removed, and a few smaller (but soon to grow) ones in place of them. (It was "experimental" in that the 2.5 kernels weren't supposed to be a part of any distribution. It eventually grew into the more mature 2.6.)
(could have sworn that was on xkcd but I guess not)