It's some friend/business associate of Michael Hart, founder of Project Gutenberg. I find the totals to be rather questionable, since all the national Project Gutenbergs collectively have far less than 100,000 books. PG USA has just under 30,000 books, and the rest have far less. In the first or second year, I looked at it and saw a huge number of duplicate editions that were generated from the original PG source. Also, most of the PDFs appeared to be generated from text sources with no attempt to regenerate the original formatting, or include images if there had been an HTML edition with images at PG.
At the time I looked at it, Google had released about a million public domain books through Google Books, and Michael Hart was sending out a lot of propaganda for the World Ebook Fair and how it had more books than Google, which IMHO was not true, and not even close to true.