What is the ruling on the machine my friend found discarded in the street during the revolution? Is it permissible for me to use it, and if not, what should I do with it given the impossibility of handing it over to a responsible authority for fear of being accused of theft?

May Allah reward you for your diligence in observing your religion. The mentioned machine belongs to the shop owners, and it is obligatory to return it to them, even through indirect means, if you fear harm. The main point is to deliver the right (the machine or its value) without publicizing it. If you cannot deliver it, then return its value or deposit it into the shop's account. If you cannot deliver the right by any means and despair of doing so, then give the value of the machine in charity on behalf of its owners.