Legally speaking, jailbreaking an iOS device has always been a grey area. Well, now it is clearer. The US Copyright Office issued an exemption to the Digital Millenium Copyright Act that jailbreaking a device does not violate US copyright law.
But it’s not a blanket ruling, because according to the US Copyright Office, tablets are “difficult to define.” The Electronic Frontier Foundation, along with many others have been appealing to the Copyright Office to make exemptions to the DMCA legalizing the customization of a device you own.
The exception was granted to allow users to use a program that’s available on one platform, but not others. And the ruling goes beyond just iPhones, and might apply to the Android platform as well. According to the document.