It can be done, and used outside of Korea...
However the requirement is that you create an LG SmartWorld account that *thinks* you are in the Korean market. You will need access to a Korean cell phone number (as that is part of the registration process).
If anyone is visiting Korea on a rented Korean SIM, you might be able to activate it that way. I was fortunate enough to have some connections there who were kind enough to let me quickly borrow their phone # for the verification process.
After that, you should be able to login regardless of your physical location, as long as it thinks your account is Korean.
On the LG SmartWorld registration screen, it explicitly states (in Korean) that the service is only available there for now.
Hope this helps