how to change language in linux version book 2 ver 1.05 ?

Unfortunately, there is no alternate language support. Some people volunteered to make a translation, but none of them ever finished. The developer decided not to pursue translations any more.

Some worked with BW on a translation but never finished, the Russian volunteers attempted to hack the game to do it themselves.

I've always wondered why none of them finished their translations. Were they out of their depth? Or were they too lazy to finish what they had begun?

I'm sure most of them were out of their depth. I've worked with professional translators. It is a much harder job than most people imagine, and there's a lot more text in an RPG than you might at first think. I also have friends who write for major game studios. LOTS of text. Getting across jokes, in particular, is not an easy thing. There's a lot of humor in Eschalon, and not all of it translates well.