Wow! That's interesting. I've rarely met any group which uses Alignment Languages and I've been puzzling over its implementation in my own game. I understand the value of having Alignment Languages by creatures who share an Alignment, but the "language" is lost when alignment shifts and another Alignment Language is gained. I know this is really tightly tied into the Alignment system as a whole, so I'm thinking it gets deeply into the answer of "What is a language?"
Quite coincidentally, I was reading the book "Cheers, Gary" (a collection of ENWorld forum posts by Gary Gygax published in book form - you can read them yourself here: http://www.enworld.org/forum/showthread.php?22566-Q-amp-A-with-Gary-Gygax-Part-I) tonight and found this question asked of Gary Gygax about this exact subject (pp78). Here's his answer:
"As for alignment languages, as I worked up the mindsets for the none it seemed to me that each such groups would have developed their own patoise as a recognition means, more or less like secret societies have signs and signals to ID their fellows.
Never did I envisage characters announcing their moral-ethical (or lack thereof) beliefs and convictions. Rather, the alignment languages were meant to be the means by which one might discover a like-natured individual. Similarly, conveyance of information or general conversation was not contemplated using such "language".
All typos and gramatical errors are by the original author

Scott