Ah yes, Esperanto, the official language of Riverworld!
Well, I just checked the CD, and there are a few passing mentions.
Apparently, "Millions Now Living" Etc Etc WAS translated into Esperanto in the 30's, with Da Judge's permission, of course. A talk was given in Europe around this time too.
Later articles, when mentioning it, comment on how it was invented so that better understanding of each other would help in World Peace, but ony God's Kingdom (tm) can bring that about, yadda yadda.
Kinda reminds me of the Babel fish from The Hitchhikers Guide to the Galaxy. Because it allowed greater understanding between the races of the entire universe, it has been the cause of the largest and bloodiest wars in history.