Is a three-column footnote layout possible?

The memoir class provides three-column footnotes. In all it provides four kinds of footnote layouts: normal, two-column, three-column, and run together in a single paragraph.

\documentclass{memoir}

\threecolumnfootnotes

\begin{document}

\null\vfill% just for the example

Some text.\footnote{Author 2001} Some more text.\footnote{Buthor 2002}
    And some more.\footnote{Cuthor 2003} Does this text ever end?\footnote{Duthor 2004}
    Yes.\footnote{Euthor 2005}

\end{document}

Warning: ledmac package is deprecated, see Update section below for correction.

As pointed out by Peter Wilson, memoir's code for three-column footnotes is based on that of the ledmac package. That is, one can enable such a layout also for other classes than memoir with the following caveats:

• Contrary to the standard classes, footnotes (here: the ones in the first column) won't be indented;

• The ledmac footnotes don't feature an optional argument to change the number of individual notes.

Also note that both the memoir class and the ledmac package permit column breaks within individual footnotes.

\documentclass{article}

\usepackage{ledmac} % see Update section below
\footthreecolX{A}

\let\footnote\footnoteA

\begin{document}

\null\vfill% just for the example

Some text.\footnote{Author 2001} Some more text.\footnote{Buthor 2002}
    And some more.\footnote{Cuthor 2003} Does this text ever end?\footnote{Duthor 2004}
    Yes.\footnote{Euthor 2005}

\end{document}

---

Update

As @LaRiFaRi mentioned, the ledmac package is deprecated and we can use reledmac package instead. To do so, we could exchange the following two lines

\usepackage{ledmac}
\footthreecolX{A}

by these ones

\usepackage{reledmac}
\arrangementX[A]{threecol}

With bidi package (well, sorry if you do not need bidirectional typesetting but it provides extensive tools for footnotes), you can typeset footnotes in 1 to 10 columns. In addition you can typeset paragraph footnotes too. Here is an example:

\documentclass{article}

\usepackage[extrafootnotefeatures]{bidi}
\threecolumnfootnotes

\begin{document}

\null\vfill% just for the example

Some text.\footnote{Author 2001} Some more text.\footnote{Buthor 2002}
    And some more.\footnote{Cuthor 2003} Does this text ever end?\footnote{Duthor 2004}
    Yes.\footnote{Euthor 2005}

\end{document}

In addition you can also control the direction of the column of footnotes. For details see the documentation of bidi package.