Note that the values for Boolean options are case-insensitive.

Doc/lib/libcfgparser.tex

@@ -166,8 +166,9 @@ A convenience method which coerces the \var{option} in the specified
 \var{section} to a Boolean value.  Note that the accepted values
 for the option are \code{1}, \code{yes}, \code{true}, and \code{on},
 which cause this method to return true, and \code{0}, \code{no},
-\code{false}, and \code{off}, which cause it to return false.  Any
-other value will cause it to raise \exception{ValueError}.
+\code{false}, and \code{off}, which cause it to return false.  These
+values are checked in a case-insensitive manner.  Any other value will
+cause it to raise \exception{ValueError}.
 \end{methoddesc}
 
 \begin{methoddesc}{set}{section, option, value}