First, let me stifle some confusion.  Dang Soo Do and Tang Soo Do are exactly the same thing.  The Korean and Chinese words are exactly the same.  The forms, techniques, history, ranks, etc... are exactly the same.  So why do we at the KDA choose to use a "D" instead of a "T"?

Simple...

The Korean government has gone through a lot of work to romanize it's alphabet, allowing better transliterations of Korean words for Westerners.  A good example of this is shown in Google Translate.  If I were to type in "" the pronunciation shows up below as "dang".  If I were to type in "" the pronunciation shows up below as "tang".  As we all know, the correct way to write Dang Soo Do in Korean is "당수도", not "탕수도".  And therefore, we use the romanization "Dang Soo Do".