register_sidebar_widget is deprecated since version 2.8

Hello there,
is there an easy way to make the widget compatible with the latest wordpress 3.8.1?
Your plugin is quite useful so it’s a shame is not working anymore.
The issue is here:

Notice: register_sidebar_widget is deprecated since version 2.8! Use wp_register_sidebar_widget() instead. in /var/www/vhosts/mywebsite.org/httpdocs/wp-includes/functions.php on line 2908 Warning: Missing argument 3 for wp_register_widget_control(), called in /var/www/vhosts/mywebsite.org/httpdocs/wp-content/plugins/registration-form-widget/registration-widget.php on line 81 and defined in /var/www/vhosts/mywebsite.org/httpdocs/wp-includes/widgets.php on line 727

I will be happy to test the fix on my site.

Regards.

https://wordpress.org/plugins/registration-form-widget/