WARNING
I wouldn't use this on retail btw... let me explain this situation a bit. (slothmo the l2.net dev told me how it works exactly)
what it REALLY does is prevent gameguard from updating. Doing so, this emulator simply blocks the gameguard updates.
all it does is emulated the gameguard update center and give back the "ok" to your client gameguard.
now, gameguard isn't only to update the program detection, its also used to send packets with extra encryption of code, its pretty much like sending a password with every packet, so lets say the password is "MYCODE" (in hex) and you wanna move to a location, now, the emulated gameguard uses an old pasword which is "USER"
theres one thing you must understand with NCSOFT, they WONT block their old packets, they will keep them all for bot detections. This is why walker usually still works.
ok, so you send a packet to move to a location. moveto 11234,123124, 123412 password = USER
BANG, your done. NCsoft can easily detect you, ok... so this user used an old gameguard, and their eula states modifying the game in any way is ILLEGAL and they can ban you. so there you are. Your on their blacklist.
yet again, you can always gamble and use it again because NCsoft is a money making company... thus losing you would mean losing a customer.
I hope this educated a few of you out there ^^