The process of modifying the software to work on a different system is legal because it is reverse engineering (though it it used DRM it is illegal by the DMCA), but distributing it is still copyright infringement.
Is this jailbreaking in general, or just carrier unlocking?
This article completely ignores video games. Right now, any PC game that can be played at 1080p can be played at 4k (well, almost any game - see Dark Souls). Once the next generation consoles hit, there will be a few games that support 4k as well.