Hi there,
WordPress was actually designed to be built without the use of any sort of third party software. As such, there is no way for additional software to be used with our services.
If you are not interested in using our Custom Design add-on, it can be canceled and a full refund can be provided within the first 30 days of the addon's life.
You can do this yourself by logging in to your account's Dashboard and then going to the Store -> My Upgrades section of your dashboard, where you'll find Custom Design in the list of your upgrades, along with a "Cancel" button.
Hope this helps, and please let us know if you have any more questions!