The issue seems to be that for some reason your server will not output the contents of the forum's output buffer. ob_start() ob_flush(). You can comment these 2 lines out in the forum's index.php and everything will work the same.
It seems like the ob_start("aefoutput_buffer"); output_callback is functioning properly (as far as I can tell) but the output from the buffer is not being displayed.
This is outside the realm of my expertise. I am no9t sure how much more time I am willing to put into this unless someone wants to give me some ideas.
Everything seems to work with the forum outside the portal.