I've seen listings on eBay for Sprint Moto X that are unlocked for use on any carrier so I believe it's possible.
I've researched and can't find any way to unlock it without a sprint account.
I've read the terms of unlocking (found here) and as far as I can tell anyone with a sprint account should be able to call up customer care and unlock my phone.
I've talked to a user on here that says if I get my phone unlocked and sent him some files after the OTA unlock he may be able to find a way to let others unlock their Sprint Moto X phones.
If someone could help me I'd be willing to send them a few bucks via PayPal.