How do I disable the free version's reminder that the search scheduler is disabled?

You can override the default behavior of the Message Module on a per app basis.

A very smart man I know did it like this (though I might use jquery's '$.each' myself):

<app>/appserver/static/application.js:

if (Splunk.Module.Message) {
    Splunk.Module.Message= $.klass(Splunk.Module.Message, {
        getHTMLTransform: function($super){
            // Ignore the following message(s)
            var argh = [
                {contains:"Search scheduler is disabled in Splunk Free", level:"info"},
            ];
            for (var i=0,len=this.messages.length; i<len; i++){
                var message = this.messages[i];
                for (var j=0,jLen=argh.length;j<jLen;j++) {
                    if ((message.content.indexOf(argh[j]["contains"])!=-1) && (message.level == argh[j]["level"])) {
                        this.messages.splice(i,1);
                        break;
                    }
                }
            }
            return $super();
        }
    });
}