After starting on Google Code, and later adding a git mirror, Emscripten has now moved entirely to GitHub. emscripten.org and so forth should now forward to there.
The main reason for the change is the inconvenience in maintaining two clones. hg-git helped greatly, but it remained a constant hassle. Meanwhile GitHub has been getting more popular and more useful. The last straw was GitHub's recent addition of a much nicer issue tracker. So I decided to make the move today, which coincides nicely with the release of Emscripten 1.0: A fresh start on the road ahead to 2.0.
Code will not be updated in the Google Code page anymore, and I pushed a final commit there to warn people they are running old code if they get there by mistake. I moved the important wiki pages to GitHub, which leaves only one thing left behind, the open issues. If you have an open issue on Google Code that you care about, please either open a new issue on GitHub for it, or tell me and I'll do it for you.