Can I Integrate This Plugin Directly Into My Theme Template?

I have a client that wants an email signup at the end of every post. I was wondering if there's a way to integrate this plugin via php into the template file. She wants the widget function, as well, but doesn't want the user to have to scroll back to the top of the page when they're finished with her often lengthy posts if they chose to subscribe.

If this can be done, what is the code?
<?php echo show_subscribe_by_email(); ?>