From what I understand, there are two forms of "Kumdo". The one most people will encounter is very similar, if not identical, to kendo, since it was taught to Koreans during the Japanese occupation (while visiting my Aunt in Korea this past summer, I mentioned I studied sword and she all of a sudden jumped forward and cried "Tsuki!", much to my surprise -- she was taught in high school during the occupation) -- after the removal of the Japanese influence, Kumdo was still practiced by some people, and though some variations have entered into the system, they aren't significant enough to allow instant discernment between the two arts. Therefore pratictioners of this Kumdo can and do participate in kendo tournaments -- most of the ceremonies are similar as well.
The second, and more rare, Kumdo is an indigenous Korean sword art. I don't know much about it being taught as its own art, but sword is taught as part of Kuk Sool Won, among other styles. Certain elements are similar to Chinese sword (jumps, elegant circular motion, a variety of stances, incorporation of kicking), and certain elements are similar to Japanese sword (strong linear cuts, the design of the weapon).
I hope this helps!
Nicholas