Welcome to the forum. Sorry, you can not post links here until you've become an active member.
To answer you questions: Friction drive bikes are those employing an engine coupled to the bicycle wheel by way of a roller or wheel that when rotated by the engine transfers power directly to the wheel.
Pushers are those bikes powered by an engine mounted in/on a small trailer or wheeled device mounted behind the rear wheel and 'pushes' the bike.
As for 'direct' drive, it is not a term we use but I'd have to assume the magazine article you read is referring to the most common method of propulsion which would be a chain drive bike whereby the engine drives a motorcycle/bicycle style of chain that in turn drives the rear wheel via a sprocket arrangement.
Hope this helps.
Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"
Last edited by 2door; 05-24-2010 at 11:40 AM.