Everyone already has a day job. If you'd like to volunteer to help upgrade the texts, we'd be happy to hear from you. A. See answer to 4. above. They look pretty reliable to me. The answer is closely related to the answers to questions 4 and 5.
People make money for producing scholarly editions.
But they are in effect hobby editions, made available by the transcriber as found in, in many cases, nineteenth century editions, and chosen by virtue of availability and lack of copyright problems. A major gopher-based collection of world classics in English, compiled by Virginia Tech, but now defunct at that site. Mirrored at the University of Adelaide Library. Texts are available there as zip archive files. Used by permission.