The message is
"Still no Half-life 3" written in 1337, with @ for spaces.
Therefore, the identity is almost certainly
Gabe Newell, or GabeN.
It may of course be someone else, but that seems unlikely. So let's try to torture the clues until they fit.
My name is Gregory, and i am a good man.
Gregory Goodman produced the movie The Gift
Extraterrestrials are involved.
Yellow natural liquid.
Oh my god !
Just Chuck Norris testing some stuff.
No testing required, it will work.
Ok, so torturing them yielded a worthless confession with no particular "classification". The Geneva convention may have been onto something.