write.skin.php 에서..
1~3째줄을

<?
if (!defined("_GNUBOARD_")) exit; // 개별 페이지 접근 불가

if ($is_dhtml_editor) {
    include_once("$g4[path]/lib/cheditor.lib.php");
    echo "<script src='$g4[editor_path]/cheditor.js'></script>";
    echo cheditor1('wr_content', $content);
}
?>
로 변경..

159~171번째줄을...

    <td style='padding:5 0 5 0;'>
        <? if ($is_dhtml_editor) { ?>
            <?=cheditor2('fwrite', 'wr_content', '100%', '350');?>
        <? } else { ?>
        <table width=100% cellpadding=0 cellspacing=0>
        <tr>
            <td width=50% align=left valign=bottom>
                <span style="cursor: pointer;" onclick="textarea_decrease('wr_content', 10);"><img src="<?=$board_skin_path?>/img/up.gif"></span>
                <span style="cursor: pointer;" onclick="textarea_original('wr_content', 10);"><img src="<?=$board_skin_path?>/img/start.gif"></span>
                <span style="cursor: pointer;" onclick="textarea_increase('wr_content', 10);"><img src="<?=$board_skin_path?>/img/down.gif"></span></td>
            <td width=50% align=right><? if ($write_min || $write_max) { ?><span id=char_count></span>글자<?}?></td>
        </tr>
        </table>
        <textarea id="wr_content" name="wr_content" class=tx style='width:100%; word-break:break-all;' rows=10 itemname="내용" required
        <? if ($write_min || $write_max) { ?>onkeyup="check_byte('wr_content', 'char_count');"<?}?>><?=$content?></textarea>
        <? if ($write_min || $write_max) { ?><script language="javascript"> check_byte('wr_content', 'char_count'); </script><?}?>
        <? } ?>
        </td>
로 변경

341번째줄에..

    <?
    if ($is_dhtml_editor) {
        echo cheditor3('wr_content');
        echo "if (!document.getElementById('wr_content').value) { alert('내용을 입력하십시오.'); return; } ";
    }
    ?>
추가하세요..