SEO is Marketing. Via the modern, primary method most people look for what they want and need (search engines).
The origins of SEO? Marketing.
The origins of Marketing? Markets.
The origins of Markets? Human civilization.
The origins of human civilization? IMHO, Atlantis.
To include buddypress widgets inside WP themes:
First, install Bowecodes so you have BuddyPress shortcodes. WordPress › Bowe Codes " WordPress Plugins
Then, either insert something like this into your theme, using the relevant shortcode:
<?php echo do_shortcode("[shortcode]"); ?>
Or perhaps, add the insertion as a function into your functions.php file. imath/functions.php
Or perhaps, instead of bowecodes, you could create a new widget area in a specific location of your WP theme. Widgetizing Themes
The output of a WordPress-generated blog and the output of purely scripted HTML pages could be exactly the same.
In other words, neither is inherently better for SEO.
Except, WordPress is by far a better Content Management System. Imagine making a change to the header of every page on your site. With WordPress, that would involve, likely, just a single new line of code in the header.php file. If you scripted and published each HTML page individually, you'd need make repeated changes to perhaps hundreds or thousands of pages -- taking hours or days to make the same change that you could make in seconds or minutes if you were using WordPress.
TL:DR; use a CMS -- preferably WordPress.