IFRAMEs have a bad reputation. I understand the sometimes confusing search engine arguments against (search links will often point to the iframe alone, rather than to the enclosing page as a whole).

However, I run a discussion forum on my boat building website that now has 20,000 posts. It's a valuable addition to the boat building community and to my website. But I want that forum to appear as the contents of a block element <div> inside my content management system (Robopages). Stripping the <html> <head> and <body> elements from the forum's *.tpl templates won't work without major php code modifications, because the forum's links are generated the wrong way (not to work as a plugin to an enclosing system) and because of conditional header branching:

if ($php_condition)
header("location: $this);
header("location: $that); .......................................this sort of thing results in chaos for an enclosing CMS

I just finished several days of work hacking a simpler open source forum so it could be used in embedded mode. But that simpler forum lacks features I want.
What ARE the arguments against simply putting my original forum inside an iframe, so it can appear as an integral part of my enclosing CMS. Even though it isn't?

If it's just the search engine argument perhaps I don't care. Why doesn't SOMEBODY make an open source forum that can indeed be embedded?