If you are looking to use a Sprint HTC device outside US, then we have some really great news for you. You can now unlock SIM of most of the HTC device from Sprint for use on any carrier out of US using the SunShine bootloader unlock tool, using its latest version 3.1.18.
Yes, outside US, meaning you won’t be able to use Sprint HTC device on T-Mobile using the SunShine tool. SunShine is a paid tool btw, that lets you unlock bootloader of various HTC and Motorola devices that are otherwise locked by the carriers with no official unlock tool made available.
To buy SunShine tool, go here (costs $25). Download the tool and make the payment, back up your device completely and then give it a run.
Btw, you will need root access on your device for SunShine to work (on 4.4.3 and lower devices), so be sure to confirm it first that root access is available for your device. Rooting will void your device’s warranty. If you are okay with that, it’s good to first root and then buy SunShine.
Also, be sure to check out the devices compatible with the tool before making your pocket lighter by $25. It’s available in the paragraph on download page itself.