byuu posted an article on his blog (byuu.org) just two days ago. His emulator was called bsnes, not bzsnes, maybe that's the source of confusion? bsnes has now evolved into higan, so that might also be why you can't find it. The higan source is mirrored on gitlab: https://gitlab.com/higan/higan

edit: sorry, wasn't aware of the (april fools) bzsnes release, realise now that I'm probably more confused than you are.

edit 2: the "original" bznes source (AFAICT) is on archive.org: https://web.archive.org/web/20151105124237/http://snesemu.bl...