Is there an attribution obligation for arXiv preprints with the standard license?
If you use someone else's work, academic honesty requires you to cite that work.  Licenses and copyright are completely irrelevant.
If you redistribute someone else's work, then the license is important.  That is a matter of law, not academic honesty.  The ArXiv license does not permit you to redistribute work unless you are ArXiv; attribution is irrelevant.  The ArXiv license also does not authorize modification, so ArXiv cannot change the author names in a paper.