Pulling posts into static site (wordpress as subdirectory)

There are several ways to do it:

  1. SQL query to the wp database
  2. Using a Restfull API plugin: https://wordpress.org/plugins/json-api/ you will get the json of the posts.
  3. Using the RSS Feed (check this tutorial http://code.tutsplus.com/articles/how-to-read-an-rss-feed-with-php-screencast–net-1272)

To be very light you can cache the results will all options.
You can grab the results and cache that results for X hours/days depending on your new posts frequency.
So it will only make the request to one of the ways above when cache time as expired.

Cheers