Well, as I understand it, JKD is a philosophy developed by BL. It is a set of concepts and principles. It's an ideal. It's personal expression. BL's JKD was different than Dan Inosanto's. And Taky Kimura's is different from either of theirs. Richard Bustillo and Ted Wong's is each different yet again from each other and the rest. Etc.
Jun Fan is a system that can be taught. It was developed by BL as a vehicle to help people find their own JKD. It's based largely on Wing Chun with influences from Western Fencing, Boxing, Savate, and others (though those 4 are the big ones most commonly heard, BL was an avid researcher of martial arts technique, history, and philosophy and drew things from a wide variety of sources in the development of Jun Fan - BL is probably the only one who could have identified everything he drew from, and he may not even have been able to since some of it may have happened on a subconscious level beneath his awareness).
"Re: Difference btwn Jun Fan Gung Fu and OJKD November 12 2003, 4:26 AM
Well, first of all, it wasn't his back injury that caused the creation of Jeet Kune Do. It was his fight with Wong Jak Man in Oakland that brought about the changes.
Jun Fan Gung Fu is basically Bruce Lee's version of Wing Chun. It consists of a bai jong position that is approximately 70/30 0r 80/20 weight distribution (depending on who is teaching it), with most of the weight on the rear leg. Footwork is primarily forward and backward push shuffle and left and right sidestep. The primary hand tools are chung chuie, bil jee, choap chuie and qua chuie. The primary kicks are jik tek, juk tek, oou tek and hou tek. There is much emphasis on four corner lin sil die dar. Don chi sao and seong chi sao are the primary energy/sensitivity drills. There is basic and compound trapping hands, consisting primarily of pak sao, lop sao, fook sao, boang sao, huen sao and jut sao. There are entering methods such as chop chuie/qua chuie and jik tek/bil jee. Jik chung chuie (the straight blast) is practiced continuously until it becomes ingrained into your neuromuscular response system. There is more, of course, but these are the basics.
Jeet Kune Do is more alive and free, with great emphasis on mobility, speed and intercepting the opponent's initial movement, or even their intention to attack. The bai jong is 50/50 weight distribution, and the rear heel is raised. There is much emphasis on quick, explosive footwork and evasive tactics. Basic hand tools are the chung chuie, bil jee, qua chuie, ping chuie, jao sao and oou chuie. There are eight basic kicks (jik tek, juk tek, oou tek, hou tek, qua tek, juen tek, so tek, dum tek). There is great emphsis on explosive gap closing, emphasizing fast, powerful lunging attacks. The primary principles emphasized are longest weapon to nearest target, power side forward, centerline preservation, hammer principle, constant forward pressure, visual focus, economical structure and no passive moves. The primary energy/sensitivity drills are don chi sao, seong chi sao, cross energy drill, lop sao cycle drill and harmonious spring drill. There is great emphasis on trapping, both simple and compound. Bruce Lee's Five Ways of Attack are always prominently emphasized (SDA, ABC, HIA, PIA and ABD). There is much use of training equipment such as the focus glove, air shield, shin guards, double end bag, heavy bag and the mook jong. There is much sparring with protective gear to develop timing, distance awareness, power transfer in movement, evasive skills and striking accuracy.
There is much, much more that I could go into here, but this should give you some ideas as to the difference between Jun Fan Gung Fu and Jeet Kune Do."
I'm not a JKD nut so you should probably ignore my answer, but...
Jun fan gung fu was the fighting system that Bruce Lee developed. It has a repertoire of movements, tactics, drills, etc. Mainly it came from wing chun, boxing, fencing, and whatever. I think mainly that's it. Jun fan was his name.
Jeet kune do is alive, it's an ideology which underlies evolving systems seeking after the truth in combat. Bruce Lee has nothing to do with what JKD is. What it was, yes, but not what it is. What it is, is Demi Barbito's CSPT (centre for self-preservation training). JKD is Vunak's PFS (progressive fighting system). JKD is Burton Richardson. JKD is Roy Harris. JKD is Matt Thornton's "Functional JKD".
From my studies into the matter Jeet Kune Do refers to two different things.
Bruce Lee developed a style (back when he believed in styles) based on interception. This was in response to his dissapointing (to him) fight with Wong Jak Man. This he termed "Jeet Kune Do."
After his back injury, he developed a philosophy for martial arts, that kept the name "Jeet Kune Do."
Jun Fan on the other hand, often means two different things. Bruce Lee taught what he termed "Jun Fan Gung Fu" which is what he was teaching before he developed the first "Jeet Kune Do" - primarily modified Wing Chun from what I understand.
It also could mean what some people refer to as Original Jeet Kune Do, or Jun Fan Jeet Kune Do, which is in reference to the Jeet Kune Do style.
This is all my findings and opinions, and I'm no expert.