Just ran across this in TSR, Chapter 31:

 

Alaana Mosvani (so probably true, right):

 

"The Children  . .  are not Darkfriends, and for that reason they are safe from the Power except in self defense." 

 

Seems he meant to include DF in the 3rd Oath for quite some time.

That has already been mentioned in the thread a few times, along with other references to the Darkfriend clause early in the books.  Also, I just noticed that RJ even clarified the issue somewhat in interviews, when discussing the Aes Sedai damane.

You mean this?

 

Robert Jordan Answers: The Aes Sedai captured by the Seanchan are indeed useless as weapons, except against Shadowspawn or Darkfriends, because they are bound by the Three Oaths, and that limits their value considerably since being weapons is a major use for damane.

 

And I've always assumed that darkfriends are included, considering the number of times it's been mentioned.