If you know when the light is going to go green (autocross, or a good guess), you can jump a little. LFS detects jumps by just seeing who's moving when the light goes green (as far as I can tell), so that first bit where you dump the clutch and sit still spinning your wheels whilst barely moving won't trigger a jump start if you do it early. You can 'steal' about .2 on autocross with good timing as opposed to reacting, and even more if you're starting on grass/dirt because it takes longer to get moving.
Having said that, he got one hell of a start in this case, more than I've ever seen. I don't know if the above would cover this example. Maybe if he was lagging during the last moments before green, the server wouldn't get any notification that he was already moving at the point it checked?