[wplug] Page translation?

[Zach]

I've seen some sites such as Audacity and GTK which do automatic page
translation. I look at the page source but it doesn't really tell me
how they are doing this. Typically it will say something like
"?lang=de" and this renders the page in German. Is "?" some PHP thing
or is that Apache specific? Does "?lang=de" tell the webserver to call
some translation script and passes "de" to it as the argument? Is
there a way I can implement this automatic translation on the client
side (I don't have control of the server side for my homepage)?
Preferably something that is FOSS.

Thanks,
Zach