Co-authors not willing to publish after rejection. May I drop them?
It depends what the co-authors did. If they were involved in the work they should normally be authors of the paper. I think the important questions you need to answer are:


What exactly do you mean by "showed no interest after repeated calls"? I have never heard of someone who does not want a "free" paper published, unless they disagree with the methods or conclusions in the paper. What is the reason they are not interested?
Did you ask them if they agree to not have their name on it? If they agree: problem solved. If not, that means they do agree to be co-authors: problem solved.