Applies to 2.0.40 too. Dirty hack for me was comment the following section in 
configure:

  if test "x$CFLAGS" = "x"; then
    echo "  setting CFLAGS to \"-DNO_DBM_REWRITEMAP\""
    CFLAGS="-DNO_DBM_REWRITEMAP"
  else
    apr_addto_bugger="-DNO_DBM_REWRITEMAP"
    for i in $apr_addto_bugger; do
      apr_addto_duplicate="0"
      for j in $CFLAGS; do
        if test "x$i" = "x$j"; then
          apr_addto_duplicate="1"
          break
        fi
      done
      if test $apr_addto_duplicate = "0"; then
        echo "  adding \"$i\" to CFLAGS"
        CFLAGS="$CFLAGS $i"
      fi
    done
  fi

/modules/mappers/config9.m4 makes configure always set NO_DBM_REWRITEMAP.

mod_rewrite has just been changed to use the apr-util dbm interface.
This change will be in the next release of Apache 2.0.x.

For now, the SDBM dbm flavor is always used.  It won't be compatible
with dbm rewrite maps built for Apache 1.3 until apr-util supports
ndbm and mod_rewrite is changed to prefer ndbm over the built-in
sdbm.   Someone has expressed to work on ndbm support soon, so 
hopefully that change will be in the next Apache 2.0.x release too.

The PR should be kept open until the ndbm support is available.

Thanks for your report, and thanks for using Apache.

ndbm support is now in.

This is fixed.