They would say no, but of course everyone "murders" some fraction of a person every day that they don't maximize their life-saving effectiveness. If they were playing video games instead to make themselves feel better, isn't that even "worse"?
People do folding because it's easy and the costs are hidden. If you could magic it out of existence, they wouldn't suddenly start donating equivalent money to maximally-efficient charities.
Of course they do; this follows directly from consequentialism, and is, in fact, an argument that could be used about donating to any charity but the most effective charity. If this was pointed to most people, they wouldn't care and would ignore it or, like the XKCD link, simply indulge themselves that much more.
That's why Folding@home is so interesting as a charity, because while most charities are simply committing sins of omission, Folding@home is committing sins of comission. (You did see the section headers, right? They aren't meaningless.)
Latest in an irregular series, some of whose previous entries were Edge.org and the Girl Scouts...
I examine the Folding@home distributed computing project with reference to the costs (electricity resulting in air pollution causing deaths) and benefits (some papers): http://www.gwern.net/Charity is not about helping. Additional data on either side of the cost-benefit is welcome.
(I also recently split out my essay describing things I have changed my mind on.)