Clarity,
This is an exploit,
Reason:
1. Yes, you can run WoW.exe twice and start two clients but you cannot log into the same account using both. By following his steps you are able to log onto the same account.
(example: account name: hm02)
If i start WoW.exe and log into hm02, i cannot start WoW.exe and log into hm02 again and play both characters.
But if i do this exploit i can.
To whoever said, whart is port forwarding, the following website is the best on the web to explain that, become an expert on your own....