That's a very misleading article. It's conflating jailbreaking with carrier unlocking, and they're two different things - in iOS community terminology, "jailbreaking" is removing software restrictions so that you have root on your own device, and "unlocking" is about carrier unlocking.

In any case, unofficial carrier unlocking isn't illegal now - it's just in a legal grey area for newer devices. See the EFF's corrections to sensationalized articles like this one: https://www.eff.org/is-it-illegal-to-unlock-a-phone