gistfile1.js

$(document).ready(function(){
    idonate.loadForm('.form-container');
    });
idonate = {
postNode : function(){

           },
serialize : function(){
              var o = {}; 
              var a = this.serializeArray();
              $.each(a, function() {
                  if (o[this.name] !== undefined) {
                    // push is for arrays... and why is push being used in a condition? what are you testing for?
                    // to make o and array you would say o = [];
                    // but you made o and object when you did this {};
                    if (!o[this.name].push) {
                      o[this.name] = [o[this.name]];
                    }     
                    o[this.name].push(this.value || '');
                  } else {
                    o[this.name] = this.value || '';
                  }     
                });   
              return o;

            },    
loadForm : function(div){
             var that = this;
             $(div).load('/sites/all/modules/idonate_custom/services-demo-form.html', function(){

                 $('form#services-demo').submit(function() {
                   var test = $('form#services-demo').that.serialize(); // that is undefined
                   $('#result').text(JSON.stringify(test));
                   return false;
                   });
                 });
           }
}