I programmed it myself, as I'm quite experienced with SMF (I started coding SMFShop back in December 2004). This uses the SMF SSI functions, and SMF's templating system.
This site uses pages inside of SMF, whereas another one of my sites (Daniel15.com) uses SMF inside another page
.
The basic code looks a bit like:
<?php
$ssi_layers = array('main');
$context['page_title'] = 'Test Page';
require('SSI.php');
?>
Hey look, a page inside the forum!
<?php
ssi_shutdown();
?>
For the menubar at the top, I modified index.template.php so it checks if it's on the website, or in the forum. If it's in the website, it shows a different menubar (the website one).
If you want to do this yourself (and don't know much about coding), take a look at TinyPortal
