create help text for a field dynamically

You can do it like this:

class ResponseForm(ModelForm):
    def __init__(self, *args, **kwargs):
         user = kwargs.pop('user', None)  # popping user from known arguments
         super(ResponseForm, self).__init__(*args, **kwargs) 
         if user:
              self.fields['ans1'].help_text = "Help Text for {}".format(user.username)

    class Meta:
        model = ResponseModel
        exclude = ('author', 'title','submit_count')

@login_required
def ResponseFormView(request):
    if request.method == "POST":
        form = ResponseForm(request.POST)
        if form.is_valid():
            submission = form.save(commit=False)
            submission.author = request.user
            submission.save()
            return render(request, 'thanks.html', {})
    else:
        form = ResponseForm(user=request.user)  # passing user as known argument
        return render(request, 'response_tem.html', {'form': form})

Here, in the view I am passing the request.user as known argument when I am initiating Form Class's Object (marked with comment). Then in the Form, I am catching the user sent from view and updating the field's help text.