WASHINGTON: Microsoft has won US antitrust approval to buy the Internet phone service Skype, the Federal Trade Commission said in a website posting Friday. Microsoft announced in May it was buying Skype for $8.5 billion, its biggest-ever acquisition, placing a rich bet on mobile and the Internet to try and best rivals such as Google Inc. The approval was announced in a listing of deal approvals that comes out several times a week. Microsoft's interest in the money-losing, but popular service highlights a need to gain new customers for its Windows and Office software. Skype has 145 million users on average each month and has gained favor among small businesses. Meanwhile, Microsoft Thursday began letting software developers imbue computers with voice and motion-sensing technology from its Kinect controller for the Xbox 360 videogame console. A free Kinect for Windows Software Development Kit opens doors for computer programs enhanced with depth-perception, voice recognition, or gesture controls using the popular console accessory. "We are looking at taking the Kinect out of the game space a bit and putting it in other spaces," said Halimat Alabi, a developer who attended a 24-hour Kinect coding marathon at Microsoft's headquarters in Redmond, Washington.