"On February 19, distributed.net began project OGR-28, the challenge to discover the Optimal Golomb Ruler with 28 marks. The previous challenge, OGR-27, is almost complete, with only 9 stubs remaining to be processed, as of February 19. People participating in that challenge do not need to update their client, as it can also process stubs for the new challenge."
But apparently they'd like to be!
http://www.distributed.net/Source#Why_is_distribut ed.net_still_not_completely_open-source_with_all_p arts_of_its_source_code.3F [distributed.net]