first thing i would think is that it's spyware and they are just going to steal your money and send you back some of it... but maybe not?
the webpage makes it sound like use everyones computer to create a massive render farm but i can't imagine something like this being used 24x7.. they articles that they link to appear to just be copies of a press release that the company issued stating that it's a "Biological Software Company" which differs from the website.
when thinking about the claims, i don't think that this is really "green" or "recycling"... you are leaving hundreds of computers turned on to only a small amount of resources on each one when you could just have a few computers turned on using all of their resources.
as for the site, i googled and found one report about the site not paying:
Ripoff Report: keep-it-on.com Green pc Non Payment ! Internet
i ran a who-is search on the site, they registered the domain name using a private service to prevent the owners identity from being known... and the do not list contact info on the site other than a info@keep-it-on email address...
it is quite possible that this is a legit small business venture someone is doing.... but given the facts i don't think i would bother with this, I don't like to leave my computers on.