Here is my definition of "a gongfu form"
It's not about height of the stances or speed of the particular movements. It's not about secret or close range 'subtle' techniques. It's about internal skill (neigong). I've read somewhere that after Yang Chengfu taught in Beijing and Shanghai many people bragged that they studied from Yang Chengfu, but within the internal circle only those were considered to be Yang's disciples who could send man flying without much obvious movement, applying short jin & nei jin. Any form of Yang style that trains that is "gongfu form" to me. Not only because of the power but because of the concomitant inner cultivation that was always part of daoist teaching.
I like the following story of Jiang Fa. Maybe it's not a real story but it illustrates my idea. When he traveled across the country and went through Chen Jiagou he saw people practicing martial art and had smiled at their movements. It happened so that Chen Changxin had noticed that and approaching Jiang Fa asked him crossly about the reason of that smile. Chen Changxin's nickname was "Family names tablet", because he looked handsome and had straight poise (like big tablet with family names). But his waist was not really flexible. Jiang Fa said that that martial art is not soft enough. Chen Changxin asked him is he a martial art adept and could he show him what he is talking about. Jiang Fa had replied that he hadn't time for that, and started going away. Then Chen Changxin decided to give the perky stranger a lesson and touched Jian fa at the shoulder. Jiang Fa just had turned back and Chen Changxin got thrown away for several meters. As the story goes on, Chen Changxin became a disciple of Jiang Fa but Jiang Fa went away for three years and told Changxin to pick up stones during that time every day to make his waist flexible (he returned after three years). If you look at the most prominent chen taiji masters (nowadays and in earlier times) they all display excellent waist flexibility and specific shenfa (body methods). Of course each taiji style has its own specifics but generally it's true for whole taiji.
Some consider Jiang Fa to be a successor of Zhang Sanfeng's art. Maybe it just means that his art contained some daoist methods.
[This message has been edited by Yuri Snisarenko (edited 04-25-2006).]