Looks like the IKO is the "International Kitesurf Organisation", but don't take it for granted!
The German Ass. you mentioned must be the VDWS. All schools in Germany and many abroad are members of it.
They also have instructor courses which are accepted worldwide.
Ryan, I think you wanted to obtain an instructor course, correct?
If yes, you should do it with the VDWS.
Next course will be in Hurghada, Egypt (25.2.-10.3.), the next in Germany in May.