I think this is where they state that in the article.
"Please note that unlocking your bootloader does not mean that you will be able to unlock the SIM lock. Unlocking your SIM lock is at the discretion of your operator/carrier and is not part of the bootloader unlocking scope."
Is what they call SIM lock the same as S-OFF/S-ON? I always heard it called 'Security-ON/OFF'.
With S-ON you can still get temp root access (until you reboot) but can not run different ROMs as it prevents access to memory locations that need to be edited to do that.
To get S-OFF on my Evo Shift(Sprint), I had to downgrade it from Android 2.3 and use an old hack specifically because it was the only publicly known way to get S-OFF. There may be better way out now.
Unlocking the bootloader was easy. I could do that with temp root on 2.3. Getting S-OFF was the tricky part for me.
S-Off gives you a permanent root with your rom. It also means you can change recoveries, hboot and all kinds of other system files and areas. It has nothing to do with Sim Lock or Unlock.
There is a FAQ question for this titled, "Why is my security still on (S-On) after I have unlocked my bootloader?":
http://htcdev.com/bootloader/faq
Basically, enough partitions are unlocked to allow custom ROMs, but not to modify the radio or modify requiring a certain carrier's SIM card (SIM lock).
No offense, but the answers here were either wrong or incomplete so I decided to look it up. For those who want the gist of the situation:
An unlocked bootloader allows for the booting of kernels that are not signed by HTC (and probably jointly the carriers).
S-OFF disables write protection on the /system and /boot partitions. It is part of the NVRAM of the radio and is patched during HBOOT, which I believe is HTC specific.
