Unhappy [Q] who do i gain write permission to htc one tmobile system directory

I'm sorry if this was covered somewhere else in the forums but i cannot for the life of me find the thread that has the stock kernel with the write permissions enabled for the /system directory of the phone. i want to be able to modify the build.op file and install busybox app. any direction will be greatly appreciated and of course ill thank you and the author of the thread if theres on already.

thanks guys your my go to for anything android and smartphone related.