SETI stands for the Search for Extra Terrestrial Intelligence.
The allegations, which first surfaced on bulletin boards and on the Ars Technica site, claim that a number of "very suspicious user accounts" with "abnormally high daily output of completed work units", are damaging the integrity of the project.
The project uses distributed computing to process efforts to search for Extraterrestrial Intelligence, as described on the Seti site, hosted at Berkeley University.
The petition asks Berkeley to "investigate these highly suspicious accounts" and take appropriate steps to prevent the alleged cheating.
You can find the petition here, while there is more information on this forum. ยต