They are real JB they even made a film more info :
http://www.luc-besson.com/fr/films/yamakasi/See also
http://www.parkour.comDavid Belle invented parkour, otherwise known as le parkour or free running. David Belle invented the sport with his friend Sebastien Foucan in the French town of Lisses, a suburb of Paris.
David Belle was featured in the BBC ident or promotional film 'Rush Hour', first shown in early 2003. David Belle describes the sport as "a way of using the obstacles found in one's path to perform jumps and acrobatics... everything must combine speed, fluidity, aesthetics and originality."
David Belle claims never to have been seriously injured while practising parkour.
David Belle, with Sebastien Foucan, formed the Yamaksai. The Yamakasi went on to find fame in 2001 as the stars of the Luc Besson-directed film of the same title.