Yes, at first I thought it was comparing against luajit, which is indeed blazingly fast. But for a compiled language just to be 4x faster than lua, I fail to see the point (of emphasizing it speed, not of the language itself).
The difference turned out to be no big deal, less than x2 in speed. The real performance killer seems to be garbage collection and chasing pointers due to inefficient data structures. Luajit doesn't help much here.
In the end we went with stock lua because it doesn't have the 1 gigabyte memory limit, and so can use a much larger thread pool.