A successful attack of Kernel.org led to the entire site being shut down temporarily as the team rebuilds the system. So, when the fifth release candidate upcoming Linux 3.1 kernel landed, there was no place to publish it.
This led to Linus Torvalds publishing the latest code on GitHub rather than on the kernel's own git repository. This makes GitHub the current, official home of the Linux kernel, but it's only a temporary solution.
"So it's been another week, and it's time for another -rc. However, master.kernel.org is still down, and there really hasn't been a ton of development going on, so I considered just skipping a week," Linus wrote announcing the release candidate.
"Since I did a github account for my divelog thing, why not see how well it holds up to me just putting my whole kernel repo there too? So while kernel.org is down for the count, let's just see how github does," he said.
Linus only joined GitHub a couple of days ago and has published the latest, pre-release Linux code several hours ago.
However, he has said that he plans to move the code back to Kernel.org, once the site goes live again, with the GitHub repository becoming a simple mirror.
In the meantime, anyone who really needs the very latest Linux kernel code, can grab it from GitHub, with a few slight changes to the regular checkout.
Kernel.org went down after maintainers decided to reinstall the operating systems on machines compromised in an attack. Hackers gained root access to at least several servers and logged username/password combinations.
It was a rather serious breach, but the method used for the hack was not particularly advanced, an off-the-shelf trojan which infected the computer of one of the people with access to Kernel.org.