L4d & L4d2 ragdolls?

Im trying to end an arguement with my freind about them. I read about them on facepunch somewhere and someone said just one can lag because they are from a different engine. but my friend says that they wont lag, that they were made for gmod and not taken from L4d at all.

can you please clear this up?

They are both wrong. They are from the source engine.

Yes, they were taken from L4D.

They will only lag if you have a shitty computer.