Runescape was one of the first major MMOs and ever since its inception the game has maintained an active playerbase. Now Jagex is going to be looking to expand that playerbase as it has confirmed both Old School Runescape and Runescape will be coming to mobile and tablet devices. Furthermore the mobile versions will inter-operable with the PC versions.
This basically means if you’re playing on PC but have to log off from that you can continue the adventure in the mobile version, and vice versa. Old School Runescape will be available first, coming this winter to mobile. while Runescape will be released at a later date.
Source: Press Release