Why it's crappy? Why you doubt it's legel? If you doubt so than maybe hacker news is also illegal because it looks like a raddit clone. (of course not)
Example in the wild: http://discuss.interviewstreet.com/
I take exception to the submitter calling this crappy. What exactly is crappy about it? I definitely see the StackExchange design but I really doubt this is even close to illegal. Since when is a QA forum idea off limits as an idea? The whole idea of StackExchange by their own admission was to create a better piece of forum software. They did it but I don't think they have a patent on it or anything.
Really, this just looks a lot like StackExchange but I don't think they're really trying to hide that. I think it's great! Has anyone heard of GitLab? It's basically an open sourced GitHub. Its awesome. This is just open source StackExchange. Still awesome.
I'm also wondering why being written in PHP is important? Is PHP not cool enough anymore? Should it have been written in Scala or Haskell or with Rails or Django? CakePHP (which is what their site runs on at least) is awesome too. Boo to this title.
There are many stackexchange clones. OSQA, shapado, coordino, and several others. The only one that can actually be installed without an infinite regress of dependencies which are no longer available (typical crappy developers who don't care about installation of their own software) is
http://www.question2answer.org/