That appears to be a Wordpress plugin, so it's probably very tailored to the WP architecture. I don't know if any parts of it can be used independently, looked to me like every file calls a wp_* function so probably not.
The general answer for this is to make a plugin. In this case you'd want a layer plugin that overrides the head_css() function, check all the files in $this->content['css_src'] and combine them. Then output a single stylesheet tag.
Take a look at the docs for more:
http://docs.question2answer.org/plugins/
