Seems to me that Free Running uses Parkour techniques.
Free Running has an emphasis on freedom of movement (tricks, flips, whatever you feel like doing, etc.) which includes Parkour techniques/movements.
Parkour emphasizes efficiency of movement.
Free Runners may be efficient at times... Traceurs/Traceuses concerned with being efficient all the time. oh heck...It is just a label. Don't worry about it. Go have fun!
Sebastien Foucan, founder (or should we say "inventor"?) of Freerunning knows the difference: in his famous 007-Casino Royal foot chase he's not fooling around with pretty/inefficient "moves".
In fact that scene has been nominated one of the 10 best Bond's moments ever as...
...THE PARKOUR CHASE
After Bond earned his 007 licence with a couple of cold-blooded kills, Casino Royale really took off with the helter-skelter parkour chase - an acrobatic relative of free running - in Madagascar. Daniel Craig's Bond chased a bomb maker into a construction site, up a building, onto a crane then back to the ground again. As in the best Bond scenes, there is time for a sly joke when the bomb maker slides niftily through a high window and, instead of following, 007 just smashes through a wall.
After the villain reaches his embassy, Bond coolly kills him and blows up half the building to escape. "In the old days, if an agent did something that embarrassing, he'd have the good sense to defect," says a furious M. "Christ, I miss the Cold War."
Freerunning, or parkour, — "the art of expressing yourself in your environment without limitations," according to Foucan — involves jaw-dropping, adrenaline-fuelled leaps, flying through the air and hurtling around urban obstacles at breakneck speed.
Im not sure about other pk groups, but Baparkour certainly does not support adrenaline fuelled,jaw dropping leaps, nor hurtling around urban obstacles at breakneck speed. I can see why this group puts special emphasis on defining what parkour is and how it should be practiced safely.
Alex, it doesn't matter the definition or differences, so long as you are practicing an art of movement, and you enjoy it, then the name is no more important than the art. You should post your reply in your discussion prompt, it will for one, lower conflicts, two better understanding, and three, bridge the gaps between these three specific forms. (Parkour's philosophies remain my favourite, but the art of displacement's goal and purpose appeal to me more.)