When I moved the Buildfarm code from pgFoundry to GitHub, I started distributing release tarballs from there too. But now GitHub has decided that they won't support that any longer. I suspect that they are being a bit disingenuous about their reasons, which probably have more to do with abuse than confusion.
I will probably move the releases to the buildfarm server - they are tiny and there is not a huge demand. But GitHub isn't the only kid on the block. They need to remember that. I know for sure I'm not the only person annoyed about it.