>Refox is just one of several decompilers. AFAIK, you can't protect against all of them.
>
>>How to protect application from decompilation using ReFox,
>>preferably for free ?
>>
>>Is it possible to apply some code to application which prevents its
>>decompilation using Refox 11 ?

When Refox originally was released it was controversial; to appeal to developers they do indeed provide a mechanism to protecting against themselves. They call it branding. However you have to own refox to use this ability.