However I've found it in another archive:
https://archive.org/details/haskell-b-compiler

On Thu, Oct 27, 2016 at 3:09 PM, Csaba Hruska <csaba.hruska@gmail.com> wrote:

Hi,

I was curious and wanted to check the HBC source code but I only found a broken link (https://www.haskell.org/hbc/hbc-2004-06-29.src.tar.gz) on Haskell Wiki.

Is it possible to fix the link? Or if somebody has the source code can you please share it?

Thanks,

Csaba