fatal error on activating plugin

i activated plugin and after adding setting frontend shows blank page.
error_log has following error.

[10-Apr-2014 07:46:12 UTC] PHP Fatal error: Cannot redeclare __() (previously declared in /home/username/public_html/wp-includes/l10n.php:146) in /home/username/public_html/products/app/code/core/Mage/Core/functions.php on line 96

https://ww.wp.xz.cn/plugins/magento-wordpress-integration/