Hi Mac. If you allow...
No, it should not be a goal in this form as it seems to you. Protostar - an outdated template and uses old technologies. Helix is the newest template and uses the newest technologies. Unfortunately, this does not have backward compatibility. Obviously, DpCalendar developers do not care about their users, forcing them to take a step back. Otherwise they would get rid of dependencies from jQuery and Bootstrap 2 and would create an extension operating in any template.
I think DpCalendar will not work normally not only in Helix but also in other modern templates.
The template is the house, extansions is a furniture. Nobody breaks and rebuilds the house for the sake of old furniture. And in this case, if you have a carpenter's skills, you take the saw and plans and customize the old furniture for the new house or hire someone for this work.