FBT Productions, a Detroit-based firm that helped launch Eminem’s career, has lost a lawsuit against Universal Music Group over royalties from iTunes and ringtone sales. FBT argued that Eminem is entitled to half the net receipts the record company gets for the downloads, rather than his standard royalties from record sales. A jury in Los Angeles rejected those claims, while awarding the producers $159,000 on a separate claim that UMG had misallocated…