This is more of a "style" of Hapkido. The founder, In Hyuk Suh, supposedly learned from his brother, In Sun Seo, who was an early student of Choi Yong Shul in Hapki Yu Kwon Sul - which formed the foundation of Hapkido. I've heard they family also studied Chinese Chuan-fa somewhere.
Every photo I've seen on the style shows some type of Hapkido-type movement. Looks very skillful. But, from the literature I've read it sounds like they are trying to minimize the influence of Hapkido and claim it comes from something during the Yi Dynasty (1392-1910AD), before the Imperial Japan invasion.
But, who knows.
R. McLain