An interesting footnote from Suối Nguồn--the recently translated version of The Fountainhead in Vietnamese--follows:
"...This needs to be distinguished from 'selfishness' as the term is usually used. The concept of acting in one's own interests is a prominent subject in the literature of Ayn Rand; because of that it is very difficult to explain fully here; we suggest you read this book in its entirety, and if possible read her other books, in order to understand clearly what Ayn Rand means in this sentence."
Just for full disclosure, I haven't completely mastered Vietnamese yet--but that is very close to an exact translation.
What I find interesting about it is that the footnote doesn't explain the sentence but simply refers readers to the rest of her works on the subject. While not that useful, the translators could easily have explained the concept wrongly--so I'm definitely not complaining!