They say imitation is the sincerest form of flattery. Try telling that to Roku (NASDAQ: ROKU).Amazon (NASDAQ: AMZN) is reportedly working on a free ad-supported streaming video service that sounds an awful lot like The Roku Channel. Roku introduced The Roku Channel in September, and it's quickly grown to become a top five channel on Roku devices as well as a key piece of Roku's strategy moving forward.Rumor has it Amazon's service, tentatively called Free Dive, will license older films and TV series.