Thats true, delays are not allowed.

AHK allows us to implement an auto-assist mechanism

relatively easily without the need to macro all of our abilities to include targeting
But he is not doing something that cannot be done with in game macros.

They are using the = key to be an assist macro, which goes off prior to his movement key.

Legal:

/assist
/move left (is there such command?)

They suggest:

Press a key which sends = (run macro with /assist in it), then sends the key bound to "/move left"

You can use a programable keyboard to send multiple keys to the client on the same keypress: i.e. "/cast lightnight bolt" thats ummm thats sending 20 keypresses by pressing one key. And obviously the t in bolt is sent after a "delay" from sending the / first. No delay allowed does not mean you cannot send keypresses in order. You just cant send nothing for a period of time. As long as you send something to the server there is no delay.

I don't know it looks legal but sure is a lazy way to do it. Why not just put /assist in all yur macros? I really dont see the gain.