Brian, my thought was that if it had its own subforum, people would be more likely to come here to talk about it, rather than it being lost in a more general forum. You know...the old "build it and they will come" approach? ;-)
Anyway, I'll try to kick some discussion off. As I see it there are basically 3 versions of the history of Panantukan that go something like this:
1. Panantukan is a historical method that goes way back in the Phillipines. It is empty hand work based upon the use of a knife, and therefore emphasizes evasiveness and lots of movement. Around the turn of the century western boxers were exposed to Panantukan and picked up on its biomechanics. This is said to be responsible for the transition from the old bare-knuckle style of boxing to what we now consider "modern" boxing. Dan Inosanto's sister wrote this up in a magazine article many years ago. But I think this version of the story is meant to make Panantukan sound more "traditional" and "respectable." I have done some research on western boxing and there are all kinds of problems and holes in this version. I don't find much at all to support it. There are plenty of good explanations of why the old "John L. Sullivan" style of boxing transitioned to the "modern" style without bringing Panantukan into it. That's not to say that some of the footwork and evasiveness that Filipino Boxers picked up from their martial arts training didn't have some influences. Ali is said to have visited an old Filipino Boxer and learned a bit of footwork.
2. Panantukan existed in the Phillipines in a general sense if not outright, and had a similar powerbase as western boxing because, again...it was based upon knife-fighting and evasiveness. As western boxing became more and more popular throughout the world, Panantukan players recognized the similarities and began to incorporate western boxing into what they were doing. This version is more plausible, but has some problems of its own. The biggest being that you just don't find much Panantukan in the Phillipines (or so I've been told). I've also been told that if you hear the term Panantukan in the Phillipines they are usual just referring to the sport of boxing.
3. What seems to me to be the most likely and the most plausible version is this: In more recent times, martial artists that had learned both FMAs and western boxing came up with a general approach that combined both and came to be called Panantukan. One of the major contributors was Lucky Lucaylucay. He and his father were both competitive boxers in Hawaii. They of course also knew FMAs. Guro Inosanto credits Lucky Lucaylucay with introducing Panantukan to his academy. I think it is likely that he was one of...if not the...key creator of the method. Another key player here was likely John Lacoste, and of course Dan Inosanto himself. Again, as I stated before, its not a big stretch. Start with a thorough grounding in western boxing, and then start adding on principles and methods from Kali empty hands...limb destructions, zoning, body manipulations, knees, elbows, etc.....and you've got modern Panantukan.
At various times individuals have said that Panantukan is not an "art", that it is just "made up" or is just a "collection of drills." Some have supported this by saying that you just don't find it being taught in the Phillipines, so it can't be legit. I think that regardless of its status in the Phillipines, it is a part of the curriculum of several of the biggest FMA academies in the US, and now has multiple videos and a book produced that cover it. This makes it legitimate here in the states. It doesn't matter to me one bit if no one is doing it in the Phillipines.
The term "Panantukan" came from the people at the Inosanto Academy. They were originally going to use the term "Suntukan" but it was felt that people would confuse this with "Shotokan." But now I see a lot of other organizations using the term "Panantukan" for their empty-hand training who have nothing to do with the Inosanto Academy. Again, this is just an indication that Panantukan is just as "legit" as any other art.