I'm developing packages that in some places use code that started off as a direct copy-paste from the R sources (this is C code). The finished code is fairly different from what I started with, but clearly uses similar algorithms / tricks as the original code, and some lines here and there are still verbatim copies.
What is the correct way to credit the R developers in DESCRIPTION? As copyright holders? As contributors / authors (though it almost seems presumptuous for me to associate them with my crappy package)? If so, should I use "R Core Team" as seems to be the standard in base R packages for authors?
I've looked in Writing R extensions, the 6/2012 R Journal article, and other places and can't quite find an answer for my use case (I may be obtuse).