Adds the option to activate a plugin only on the main site to the network admin plugin install screen

activate-plugin-after-install.php

<?php
 /*
 * Plugin Name: Activate Plugin After Install
 * Description: Adds the option to activate a plugin only on the main site to the network admin plugin install screen
 * Plugin URI:  
 * Version:     2013.05.18
 * Author:      Shea Bunge
 * Author URI:  http://bungeshea.com
 * Licence:     MIT
 * License URI: http://opensource.org/licenses/MIT
 */

function activate_plugin_after_install( $install_actions, $api, $plugin_file ) {
  return array_merge( array( 'activate_plugin' => sprintf (
		'<a href="%1$s" title="%2$s" target="_parent">%3$s</a>',
		wp_nonce_url( admin_url('plugins.php?action=activate&plugin=' . $plugin_file), 'activate-plugin_' . $plugin_file ),
		esc_attr__('Activate this plugin'),
		__('Activate Plugin')
	) ), $install_actions );
}

add_filter( 'install_plugin_complete_actions', 'activate_plugin_after_install', 10, 3 );