It doesn't hook into the game though, the overlay is just an overlay. Although it does give people an advantage competitively :O That means it's a form of cheating by their EULA.
*So aruably is playing with textures/skins, binding keys to do anything involving timing, tweaking the interpolation timing, having a better connection, having a faster computer, being born with the normal prequisite number of fingers and toes... You get the idea.
Well no, because the scripts are part of the game and aren't a 3rd party program, they are commands in game. Textures and skins are as well, although in CSS you used to be able to create transparent skins making a undetectable wallhack. It has to be a third party program, and I'm pretty sure it has to be interacting with the game somehow. I believe that most aimbots mimic hardware inputs to the game, hence they 'hook' into it. I was never really sure how ESP (Extra-sensory perception) works, does it modify texture files? I don't have a clue.
Since mumble has no interaction with the game then it isn't covered by the EULA i guess :3