Update: Another developer, Chainfire has released an Android app to find the unlock code of the phone. It automates the tedious procedure but will come with an unlock code. You need root, of course.
Admittedly, not as easy as buying an unlock code from the web but if you’re comfortable with a bit of tinkering with the system files of your Galaxy S II, you can unlock the phone for free. You’ll need a rooted Galaxy S II to extract the nv_data.bin file and then follow the instructions stated on the source link below.
As goes with every hack, proceed at your own risk.
An easier software solution will be released in few days.