How to Play as TF2 Characters in GMOD?

Many of you have seen this video: http://www.youtube.com/watch?v=Hb5z3paDJSI&feature=fvst

In the video you can see TF2 Characters been played in various HL2 maps.
First i thought it was greenscreened, but i was wrong.

I tried searching gmod.org etc.
Does anyone know anything about this?

TF2 gamemode I assume http://www.facepunch.com/showthread.php?t=755095

Obviously the TF2 gamemode.
Shit rate me clocks.