Case 1: I am allied with The Kongo, meaning we have open borders. Our cities are very close. Many of his units are just laying around within my lands. I have no units in his lands. However, he hears one soldier sneeze and gets paranoid and asks what my intentions are. I mean, we are ALLIES. The AI should welcome my units within or to cross its lands. Case 2: Another AI says what are your troops doing on my doors step. I say we just passing through. A couple of turns later, I get open borders and my units walk through to explore, although not scouting units (but really, what is the essence of open border!?). I then get a YOU BROKE THE PROMISE notification. (Insert wtf meme). The troops on the border thing should not be an issue during being an Ally or open borders. Or friends for that matter.