The new project sparked his interest
In case you haven't heard there's a new Unreal Tournament in the works, and part of its development process will be a result of fan input. Currently, former developers are expressing interest in the new project by the droves, and the newest face in the crowd is Kevin Riepl, who composed Unreal Tournament 2003 and 2004.
This follows Alexander Bradon and Michiel Van Den Bos, who composed the original game. Nothing may come of this, but it's nice to know that all of these people are still on good terms with the series and wants to be a part of it.
ut2004 music composer (Kevin Riepl) is 'interested' [Unreal Engine Forums]