It looks to me like the script modifies the iframe element, and so must be entered in to the dom after the iframe (not in the head). So I think that your demo the iframe is running without being modified (maybe thats ok). The alternative would be to rap the html in script macros as in your example http://fiddle.tiddlyspot.com
<iframe name="CHATBUTTON_CHATBOX" id="CHATBUTTON_CHATBOX" src="https://www.chatbutton.com/chatroom/18383458/" width="300" height="450" marginwidth="0" marginheight="0" frameborder="0" vspace="0" hspace="0" allowtransparency="true" scrolling="no"><a href="https://www.chatbutton.com/chatroom/18383458/">Enter Chat Room</a></iframe> I don't think the js script worked anytime. You have tagged it :/tags/RawMarkup - missing the $ sign
Seriously, thank you. I'll check this out when I get home, later.