I'm still waiting for aggregation of update messages so that I can follow way more stuff, but github is one of my favorite sites on the net already...
Well, they could, but they'd have to move to www.github.com exclusively, wait for all those session cookies to expire or for folks to visit and get them reset...
I didn't say anything about JavaScript being disallowed, the cookies are HttpOnly. So I said that you can't do things on the server.
What mojombo said is accurate. (He's a GitHub co-founder and I'm the person who wrote the redirect code.)
A friend of mine is a web developer and he's got a shocking dynamic site that the server treats as entirely static. He accomplishes this with JSON callbacks.
(P.S. For a good time, click on the white background box or the "3N" logo when you're using are recent webkit nightly. Ian has a... ironic sense of humor.)