When you type in some querying strings the backend just fails, for example:

http://inf.demos.dam.io/sdfsdfs

I have yet to find a pattern, but I guess the author did some sort of hashing to the query string and use the hashcode as the seed to generates random text. For some given strings, the backend fail has to do with the use of the hashcode probably. (e.g. use [some_variable_or_constant_here]/[hoshcode - CONSTANT], when hoshcode == CONSTANT, the backend code does not contain the exception handling code.) Just a guess.