If they note the copyright in the source code and/or whitepaper, it's not a rip off.
This is the purpose of open source software. They can take the code and do what they want to it as long as they give the copyright to the correct sources on the code that they copied.
There is nothing wrong with what they are doing, so please don't attack them for that. Your opinion on if it may be a potential scam is your opinion. I am wary of the coin myself due to the recent ICO and dynamic PoS scams.
But don't attack them for using open source code.
Copying the source code and giving credit in the codebase is one thing. They are using the same copywrite as SDC in their ANN to explain the technology that SDC pioneered while rebranding it "Stealthcash" instead of "Powered By" Shadowcash or ShadowSend. Any linux distribution can be used as a primary example of how to properly use open source code and cite references. For example, Ubuntu references Linux same like any distribution that uses it on their "About Ubuntu" section. They don't claim credit for creating linux only attempting to improve upon it in their own way. The "about" section on any open source project's website is a similar equivalent of an ANN on Bitcointalk.
The SDC team as a whole wrote the descriptions to promote and describe this project in the ANN thread. Whenever someone uses someone else's text they should cite a reference otherwise it's plagiarism.
Any competent developer would know know to cite references. It's common sense.. something people learn in primary school. I'm labeling it as a scam because if the developer is promising development when he hasn't even learned how to cite references then his motives are clear. Plagiarism is a form of intellectual theft.. scamming the audience into believing they wrote the work.