Since fontspec is being loaded, you need to process the example with xelatex; however, the original code won't work as expected (using xelatex) and will produce the error message
) Runaway argument? \q_stop \exp_args:NNo \group_end: \iow_term:n \l__iow_wrap_tl \iow_term:n \ETC. ! File ended while scanning use of \__iow_wrap_loop:w. <inserted text>
\par l.269 \luatex_if_engine:T
{ \RequirePackage{fontspec-luatex} \endinput } ?
in order for the example to work (at least in TeX Live2012) it's necessary to load fontspec before devanagari (and the fontenc and inputenc packages should not be loaded):
\documentclass[10pt]{article}
\usepackage{fontspec}
\usepackage{devanagari}
\usepackage{bera}
\title{{\dn vivekachoodama.ni}}
\author{Sri Sankaracharya}
\begin{document}
\maketitle
\begin{flushleft}
{\dn sarvavedaantasiddhaantagocara.m tamagocara.m | \\ govinda.m paramaananda.m {sad}guru.m pra.nato.asmyaham || 1}
\end{flushleft}
\end{document}
This produces the following output:

and a warning about some fonts not being available:
LaTeX Font Warning: Font shape `EU1/fve/m/n' undefined (Font)
using `EU1/lmr/m/n' instead on input line 11.
Not loading the bera package suppresses the warning.
If you want to process with pdflatex, remove the fontspec package (and you can again load fontenc and inputenc):
\documentclass[10pt]{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{devanagari}
\usepackage{bera}
\title{{\dn vivekachoodama.ni}}
\author{Sri Sankaracharya}
\begin{document}
\maketitle
\begin{flushleft}
{\dn sarvavedaantasiddhaantagocara.m tamagocara.m | \\ govinda.m paramaananda.m {sad}guru.m pra.nato.asmyaham || 1}
\end{flushleft}
\end{document}
This time no warning is produced.