\newcommand\@authors{}
\renewcommand\author[1]{%
  \g@addto@macro\@authors{{#1}}%
}
\newcommand\printauthor{%
  \let\next\relax
  \expandafter\print@author\@authors\@nil\relax\relax
}
\newcommand\print@author[3]{%
  \ifx\@nil#1%
    \let\next\relax
  \else
    \ifx\@nil#2%
      #1%
      \let\next\relax
    \else
      \ifx\@nil#3%
        #1\ifx\next\relax\else,\fi\ and #2%
        \let\next\relax
      \else
        #1, %
        \def\next{\print@author{#2}{#3}}%
      \fi
    \fi
  \fi
  \next
}

빠르고 안정적으로 동작하는 코드입니다.