HTC has quietly updated its bootloader unlocking tool to support many older Android devices, and is working to support even more.
We were pretty excited when HTC announced that it would unlock its bootloaders for easy device rooting, but it was originally only available for brand new phones. HTC now says that all phones manufactured in the last few months should be compatible with the tool, as well as many older phones, too:
All HTC Android devices launched after September 2011 are unlockable. The website will be updated accordingly to reflect this in the coming weeks. We continue to work on models launched prior to September 2011, please check back often for the status of older devices.
Try it out on your device and let us know if it works!
HTC Unlocks Its Verizon and AT&T Bootloaders [XDA Developers]