I started running SETI@home back in 2002 on a whim, as it involved the search for extraterrestrial intelligence, which I had an interest in at the time (and still do.)
SETI@home and Astropulse are funded by grants from the National Science Foundation, NASA, and donations from SETI@home volunteers. AstroPulse is funded in part by the NSF through grant AST-0307956.