Q:

Why does the Czech translation of "Till we have faces" mean the opposite?

The title of the book Till we have faces by C. S. Lewis is translated into Czech language as Dokud nemáme tvář. I would translate that into English literally as "While we don't have a face" or "Until we don't have a face", which is not very clear. But in both cases, it is the opposite of the original English name.  
EDIT (based on comments):
The Czech world dokud can be translated as both until or while. I know that in English until and while is not the same. 
My presumption, that the translations means the opposite is based on the fact that in one language the title is about having a face, while it is about NOT having a face in the other.
Why would that be? Does it make sense somehow? Or is it just a mistake?

A:

The choice of the translator is likely to be their interpretation or possibly even a regional colloqualism to deliver the spirit of the original.
I have a comfortable working knowledge of several Western European languages but was stumped when I started doing business in the Baltics and Balkans. The negative use a more complex nuance (or perhaps simply subject to a different linguistic philosophy) and their negatives would either be non-existant or doubled up.
In addition, the concept of pending time is also distinct. Many of the speakers when using English would muddle "until", "while" and "by" for timing.
I'd suggest that the translator considered the end result that Lewis wanted and foudn the most natural Czech phraseology. Therefore he turned the phrase from a future conditional to a present subordinate with a similar outcome, e.g. "till we meet each other again" vs. "whilst we're apart".

