Use Editorial Calendar on any other page within any other plugin

I want to show Editorial Calendar on my custom plugin’s page,
so how to do that?

Plugin available on
http://wordpress.org/support/plugin/editorial-calendar

Now I tried to include edcal.php (plugin page) but its showing me Cannot redeclare class EdCal in due to two time declaration of that class, so now hot to display same plugin page on my page?

I tried include( plugin_dir_path( __FILE__ ). 'edcal.php');