Hey BeuTube,
The backend is all vbulletin. Any CMS will let you do the same thing. 90% of the changes I make on this site are through an admin control panal using html template editors vbulletin comes with.
The MA site not complex. HTML, CSS and a little jquery, and it's all custom pages through vbulletin. vbulletin has an option to allow domains access to external content, that's what I'm doing for the recent/news posts on the homepage. The login form is code I copied from vbulletin. The hardest part is making a new header and footer, but it's very easy to replace the entire header in vbulletin with whatever you want.
Vbulletin isn't the end all of forum/website software, but I use it because I've been using it for years and I can move around comfortably.
Here's another example of how far you can with vbulletin.
www.audinow.com. Mind the spam, it's 100% vbulletin forums with custom pages, same deal as here.
www.rcgeeks.ca is wordpress, customized a lot. The forums are vbulletin with the wordpress header/footer.
http://www.rcgeeks.ca/forums/register.php. It's hard to tell it's wordpress. We use wordpress at work to develop fully functional websites for big brands. Free, fast, easy.
phpbb is good, but you have to be very careful and keep up with patches to avoid disaster, and spam management can get tricky. At least the price is right.
I stay as far away from code as I can. If you know what to copy and where to click, you'd be surprised as to what you can do.
