I found a alpha/beta of Quake 1 here (with sources,progs, mac os version & etc):
http://untitled-game.com/

That's not a beta at all. It's just some weird "indie" game based on Quake 1.

My friend thinks that this is alpha. And I think that fake, due to very strange effects.

More precisely, its a pre-alpha of an unfinished game, based on quake 1 engine (the interesting thing is, most of the sources were edited when q1 engine wasnt free-for-all yet)

Looks very convincing but its not quake 1.Just like the others said,its based on the quake 1 engine.

Did you even look at the date of the last post?