Developer edition already comes with an unlocked bootloader. You don't have to unlock it.
---------- Post added at 05:49 AM ---------- Previous post was at 05:36 AM ----------
If you want to verify then just follow these steps... Confirm that fastboot option under Power settings is disabled. Completely power off the phone. Boot into HBOOT by pressing and holding the volume down and power buttons simultaneously. Once you are in HBOOT you confirm the unlocked status of the boot loader.