Andrew Gower is the founder and former owner of Jagex (and RuneScape, of course). Exactly why did he leave? We don't know, except that he has now created a new company that's also involved in making games:

From a recent job posting: "Fen Research was formed by Andrew Gower, and Jagex Ltd, the creators of RuneScape, in late 2010 to create a ground breaking and ambitious new product. Not content with creating the largest free MMO in the world, Andrew is eager to conquer a whole new arena with Fen."

Fen Research