Added a copy of Firebug Lite for debugging purposes. License is uncertain but being treated as MPL. (If is is not MPL then it is under something more permissive that permits relicensing anyway)
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>{#paste.paste_text_desc}</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<script type="text/javascript" src="../../tiny_mce_popup.js"></script>
<script type="text/javascript" src="js/pastetext.js"></script>
<base target="_self" />
</head>
<body onresize="resizeInputs();" style="display:none; overflow:hidden;">
<form name="source" onsubmit="saveContent();">
<div style="float: left" class="title">{#paste.paste_text_desc}</div>
<div style="float: right">
<input type="checkbox" name="linebreaks" id="linebreaks" class="wordWrapCode" checked="checked" /><label for="linebreaks">{#paste_dlg.text_linebreaks}</label>
</div>
<br style="clear: both" />
<div>{#paste_dlg.text_title}</div>
<textarea name="htmlSource" id="htmlSource" rows="15" cols="100" style="width: 100%; height: 100%; font-family: 'Courier New',Courier,mono; font-size: 12px;" dir="ltr" wrap="soft"></textarea>
<div class="mceActionPanel">
<div style="float: left">
<input type="button" name="insert" value="{#insert}" onclick="saveContent();" id="insert" />
</div>
<div style="float: right">
<input type="button" name="cancel" value="{#cancel}" onclick="tinyMCEPopup.close();" id="cancel" />
</div>
</div>
</form>
</body>
</html>