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Why does this site say (at the bottom, under the license) Based on a work at http://jstherightway.com. ?

I noticed that PHP The Right Way (the inspiration for this site) says something similar: Based on a work at www.phptherightway.com.

Since it's on Github - I guess it's for anyone who might fork and modify it, so that there's a link back to the original:

Ah, that makes sense (as does the answer given by sjs382). Thanks.

Is it because it's CC BY-NC-SA? And showing you how they prefer to be given attribution?