Quoted from the Runescape Knowledge Base
Quote:
6. What is AFK training?
AFK training is Away From Keyboard training. While you are playing on our games, you must be at the computer. Away-from-keyboard training is not allowed, and you should log out when you leave the computer.
To keep RuneScape enjoyable for everyone, please observe and follow our rules. We will not tolerate disruptive players, and if you break our rules your account is likely to be banned or muted. Members who are banned or muted for breaking our rules are not entitled to any sort of refund.
It says nothing about runescape being the one thing on your screen. They understand some training is monotonous and people like to distract themselves with youtube videos or browsing the fourms, why else would they increase the logout timer from the old 1:30 to 5:00