Just found this site that IMO is very useful. I don't know if this new or old. but whether it is old or new, it does serve its purpose. and the great thing is, its free Code: http://plagiarisma.net/
You can check for Dupe content by putting text within quotes ("your text") and then searching in Google.As per my observation the website mentioned by OP does the same.
copyscape is still the king imo, I used this tool on a bought article and it found it unique but with copyscape it went non unique... but nice share
There's also a new site that's in beta called percentdupe dot com. Not sure on how accurate it is but its free.