A friend posted this on my Facebook page today (thanks, Chris P.!). I think singing "Happy Birthday to You" will soon be replaced by this song. It would do away with any worries about having to pay compensation to the copyright holders.
I must say it's strange that the only place I could find this particular Saturday Night Live sketch was on sites based outside of the US. Do Americans have something against this sketch or Tenacious D? It wasn't even on Hulu, where you can find practically everything from every SNL show. Weird.