Just what the title says. It doesn't have any mention of Piriform on it, and the version it offers is behind what comes from Piriform.com but at some point I seem to remember it being legitimate.
According to these it's deemed as being not safe:
McAfee SiteAdvisor: http://www.siteadvisor.com/sites/ccleaner.cc
Web of Trust ("WOT"): https://www.mywot.com/en/scorecard/ccleaner.cc