How to enqueue some javascript source once per page

The best way to do this is to use wp_localize_script(), it serves exactly the purpose you are mentioning: passing strings to Javascript from PHP. You can do all sorts of interesting things with that: as a rule of thumb, use that when you want PHP to communicate with Javascript.

In your case you want something like this:

$ritc = array( 'initialize' => '63864593a4153879' );
wp_localize_script( '{your_script_handle}', 'ritc', $ritc );

In this way you can call ritc.initialize in your Javascript.

Be aware that you must use wp_localize_script after you have enqueued your script and passing your script $handle as a parameter.