I'm not sure how long this has been the case, but the variables that this plugin updates are automatically updated by WordPress when viewing an HTTPS page, so this plugin is no longer needed.
However, there are plugins that properly use variables such as siteurl but still deliver insecure content (i.e. serving http://example.com/js/main.js on https://example.com/) which makes the page insecure.
Also, WordPress does not update images inserted into posts with HTTPS when the page is viewed via HTTPS which also makes the page insecure.
I've developed a plugin that fixes both issues. You can find it here - http://wordpress.org/extend/plugins/wordpress-https/.